optispark ignition info



optispark ignition info

Postby grumpyvette » October 31st, 2008, 11:50 am

Image
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The yellow circle shows the area where the coil and ignition control module are located. The coil is the part with the coil wire attached. The coil wire end looks like a spark plug wire end going to a distributor.

http://www.rockauto.com/ (has good prices)

Image
Image
Image

viewtopic.php?f=44&t=758&p=1087&hilit=opti+crap#p1087

http://www.gmhightechperformance.com/te ... index.html

viewtopic.php?f=62&t=758&p=1087#p1087

http://www.corvetteactioncenter.com/tec ... spark.html

http://www.saccitycorvette.com/LT1-SBC-IGNITION.html

viewtopic.php?f=70&t=369

http://www.delteq.com/

http://www.carcraft.com/howto/ccrp_0603 ... index.html

viewtopic.php?f=70&t=369&p=3338&hilit=opti#p3338

viewtopic.php?f=36&t=628&p=839#p839

http://www.vetteweb.com/tech/vemp_0611_ ... index.html

http://www.fierolt1.com/lt1_95_up_OptiReplace.htm

http://spideraccessories.stores.yahoo.n ... 90030.html

http://www.diyautotune.com/tech_article ... t4_l99.htm

http://www.msdignition.com/uploadedFiles/MSDIgnitioncom/Products/distributors/8381_instructions.pdf

http://www.corvettefever.com/howto/16758

http://corvetteactioncenter.com/tech/c4/optispark.html

http://www.dynotech-eng.com/dynaspark.htm


http://www.dynaspark.net/products/

http://www.dynotech-eng.com/dynaspark.htm

http://shbox.com/1/component_location_views.html
optional replacement
http://www.delteq.com/

Image

The Opti-Spark system relies on two signals generated by an optical sensor pair and a timing disk. The sensors produce a high-resolution signal of 180 pulses per crankshaft revolution (for ignition system accuracy), and a profiled low-resolution signal. The low-resolution signal is profiled so that the ECM can determine the position of the #1 cylinder. The low-resolution profile gives a one-degree pulse every 90 degrees of camshaft rotation, separated by profiled pulses, which are approximately 6, 12, 18 and 22 camshaft degrees in duration respectively, and are also spaced 90 camshaft degrees apart. They occur in alternate sequence, first a short pulse, then a profiled pulse, followed again by a short pulse. Due to the alternating sequence of low-resolution pulses, the ECM receives a low-resolution pulse every 90 degrees of crank rotation.
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obviously an LT1 regulates its own ignition timing and uses knock sensor, and programable CPU input and the crank sensor unlike the L98 with it HEI but both system need you to check /verify they are operating correctly.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: optispark ignition info

Postby grumpyvette » November 24th, 2008, 8:24 pm

Failure symptoms:
Engine dies suddenly and won't restart
Engine starts, but dies, or breaks up almost immediately
Extensive cranking needed to start engine, with it almost catching
Rough idle
Sputtering under load
Backfiring
Trouble reaching high RPMs
Black smoke from exhaust
Poor performance once engine is warmed up
Weak or intermittent spark at plugs
On OBDI engines codes 16, 36, 42 may be set, but not always.

Optispark-Understanding and Modifying:
http://www.gmhightechperformance.com/te ... g_modifyin g/index.html
http://www.delteq.com/

The replace the OPTI-CRAP-IGNITION OPTION

BTW
IF your seeing arcing in the engine compartment at night, it may be well worn ignition wires, a bad cap or a wet ignition,because they are a P.I.T.A. to get to many guys don,t replace them untill they are in terriable condition,

Youll want to replace the wires ,good quality wires that are routed correctly(so they don,t touch headers) won,t arc,if everything else in the systems functioning correctly and btw you can more easily access the opti-crap cap to install new wires with the car up on a lift, yes its still a P.I.T.A. to get to but its much better than trying from above leaning over a fender.
but if your seeing arcing down near the opti-crap its either a loose wire or an indication the opti-spark might need routine maintinance (like a cap, rotor)or a rebuild.

heres good wire for an LT1

http://store.summitracing.com/partdetail.asp?autofilter=1&part=TAY%2D91025&N=700+115&autoview=sku
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: optispark ignition info

Postby grumpyvette » November 22nd, 2009, 1:56 pm

picture of defective opti after water damage posted by
http://para.noid.org/~muttvette/opti.html
wingman50
Image

Image
btw

1992-94
http://www.summitracing.com/parts/MSD-8381/?rtype=10

http://static.summitracing.com/global/i ... m28625.pdf


http://www.the-reeds.com/optispark_conversion.htm

The
Optispark is the distributor that was installed on all late model LT1's
and LT4's. This distributor was installed on :

1992 - 1996
LT1/LT4 Corvettes (Y-Body)
1993 - 1997 LT1/LT4 Camaro's, Trans Ams
(F-Body)
1994 - 1996 Fleetwood (D-Body)
1994 - 1996 Impala, Caprice,
Roadmaster (B-Body)

The concept of the Optispark was a great idea.
It allowed for very accurate control of the spark to each plug. The cap
and rotor were pretty basic in design, however the heart of the Optispark
was the LED/disc setup. There were 2 LED's that controlled the spark and
timing of the engine. Additionally, it was mounted to the CAM which
greatly assisted in giving an accurate position of TDC/BDC.

The
problem however was just that. The location of the Optispark. It allowed
road dirt, grime and water to attack the Optispark. Because of its
location, it had to be mounted behind the water pump and the balancer
making removal very time consuming. Dealers can charge upwards of $1200
to simple change a distributor. Additionally, water pumps as we know
fail. When they go, more times than not the pump starts with a small
leak. Because the water pump is located directly above the Optispark,
guess what? Another source of damage. This is by far the worst. Water
from the road MIGHT dry out. Antifreeze won't, and will instantly damage
it!

Finally, from 1992 - 1994 the Optispark was what is known in
the gearhead world as "unvented". The reason it is called this is
because it does not have the vacuum hoses connected like the newer 1995+
LT1/LT4 engines have. What the vacuum hoses do, is they pull the moisture
out of the Optispark.

What a lot of people don't realize is the
unvented Optisparks are actually vented!! Yes, they have 3 weep holes at
the base of the Optispark to allow moisture to escape. Well, all this
does is pull moisture back in. Put cold water on a hot Optispark, it's
going to suck the water in! This is the BIGGEST problem with the design.


Before you go out and buy a brand new 1995+ Optispark, be
forewarned. You CANNOT bolt a 1995+ Optispark up to a 1992-1994 LT1. The
CAM is different. You could change the CAM, timing cover, CAM gear, etc
but this gets expensive, and is very labor intensive.

So, what is
the solution?

You can do 1 of 2 things :

1. Change the
Optispark out and be up and running again. However you risk damaging it
again. There have been people who have had to replace a brand new
Optispark because they got them wet.

2. Change the Optispark out
with a modified unit.

The conversion process is
simple!

Buy a older style Optispark (the one you're supposed to
buy), and simply change the cap! Of course you will need to do a few
additional things.

Here is a listing of parts you will need
before you begin :

GM Parts :

Optispark for 1992-1994
LT1's PN - 10457702
Cap and Rotor kit PN - 10457735 or
1995+
Distr. rebuild kit (Pep Boys or NAPA)
1996 Vacuum Hose Kit PN -
12556174 or
1995 Vacuum Hose Kit PN - 12555323

Order GM
parts from http://www.gmpartsdirect.com/ or from your local GM dealer
(yuk!).

Other Parts:

Inverse Torx Bit - E4, deep well!!
SnapOn part number STLE40 - I stopped a truck, or you can order online at
http://www.snapon.com/
2-claw puller - Autozone
2 water pump
gaskets
Gasket Sealant
Vacuum T or a brass T that will screw into
the manifold
Long Breaker bar, or torque wrench
Brass fitting for
the base of the Optispark. I got mine from the local parts house that
carries various hose/pipe fittings.
3/16" Drill Bit (slightly bigger
than the hole your drilling out)
Bandages

Recommended :


Plugs and Plugwires
Converting the new Optispark

Remove
your cap from your new Optispark. Nothing like taking apart something
brand new eh?
Remove the rotor from the Optispark. This is a torx T15
I believe.
Carefully remove the rotor, and the metal disc. Do NOT
remove the slotted one! It's spot welded on for a reason. Only the disc
directly behind the rotor should be removed.
Remove the middle spacer.
This is the center portion of the Optispark body.
Set aside
everything, but the back plate. BE careful when handling this. Try not
to get any grease, dirt or anything on the disc.
You will notice 3
holes on the base. Fill the center one, and the one closest to the long
pointed portion of the base in with JB Weld or something similar. I
drilled out the remaining hole. Try not to get the metal shavings in or
on the Optispark. Next I tapped in a brass fitting. Do not use the
center hole for this, as it won't clear the balancer hub. IF you can
find a brass L fitting, this would be your best bet. I wasn't able to
find one small enough, so I used a straight brass fitting from a local
parts house.
Vacuum the metal shavings from the previous step. MAKE
sure it's clean before you put it back together.
Reassembly is the
same. MAKE SURE you don't forget to put the metal disc back in place.
If you leave it out, the gap for the rotor and cap will be WAY off. The
rotor and disc are keyed, but still make sure you put them in correctly.

Remove the old RTV Sealant, and put some new RTV on the cap at the
electrical connection. Put it back together with the newer style cap.

Lightly blow into one of the hose connections while closing off the
other. You should hear no hissing.
You aren't supposed to turn the
shaft on the Optispark (why I don't know), but I would still recommend
slightly turning it (1/4 turn is enough) to make sure everything spins
smoothly.


The Nitty Gritty

First disconnect your
battery.
Drain your coolant. Be sure to open the bleed screws. This
will help it drain much quicker.
Remove the rubber intake bellow.

Remove the upper radiator hoses.
Disconnect the bottom radiator
hose from the water pump.
Remove the coil wire, and the electrical
connections from the Optispark and water pump.
Pull the belt tensioner
out of the way, and loosen the accessory belt.
Remove the water pump.
There are 6 bolts holding it in place. Additional coolant will dump out
when you remove the drivers side lower bolt. Clean the old gasket material
and set the water pump aside for now. You MIGHT need to remove the coil,
but I didn't need to. Check the weep hole on the water pump to make
sure it's not damp.
This is the fun part (for me at least). Remove
the 3 bolts from the balancer. The Haynes manual says you can simply pull
it off without a puller. I was not able to. I had to use a 2-clawed
puller. I got mine at Autozone. I believe the one I got was the 6".
Somebody is borrowing it as we speak for this repair! MAKE SURE you make a
note of the position of the balancer in relation to the hub. Both the hub
and balancer should be marked, but not keyed.
Remove the remaining
plug wires. If they are old, you may want to replace them. Now is the
time to do it!
Remove the 3 bolts that hold the Optispark in place.
Pull it straight out. There is a shaft that connects the Optispark to the
Cam gear. This may or may not come out with the Optispark.
At this
point, you should look at the old Optispark and make a mark of where the
notch (spline) is. This will assist you later.
This would be a good
time to put some gasket sealant on one side of the gaskets, and place them
on the water pump so they can dry. This will make reinstalling the water
pump much easier.
With the old Optispark to compare, rotate the shaft
on the new one until they match up.
I found it easier to insert the
shaft on the cam shaft, and then sliding the Optispark on top of it.

IF there is any gap on any of the 3 mounting screws, you probably
haven't lined the Optispark up correctly with the spline on the shaft. It
should slide all the way on with no gaps on any of the mounting areas.
Tighten the bolts, but do not over tighten.
Run your vacuum lines.
The clip goes on the alternator bracket. MAKE SURE the hoses are going to
clear the belt.
The hose that has the filter and regulator is the
vacuum supply.
Poke a hole in the rubber bellow (on the top) and push
the L into it.
Put a T or something similar on the drivers side intake
manifold, and hook the vacuum hose up.
Reconnect the plug wires.

Reinstall the 3 bolts on the balancer. Tighten the bolts to 60
Ft-lbs. Make sure you line it up properly (see step above where you
removed it)
Put gasket sealant on the remaining gasket material, and
reinstall the water pump. Tighten to 30 Ft-lbs.
Reinstall the belt.
It is much easier to do it now before you do the next step!
Reconnect
all the hoses, the coil wire and the other misc electrical connections
(temp sensor, Optispark connector, etc).
Lightly tighten the bleed
screws.
Refill the cooling system until it is full. Place a rag
around the bleed screws, and bleed off the excess air. Don't let any
coolant get on your new Optispark!
Check and recheck everything.

Fire it up.
If everything looks good, your done!
You should
also pull the hose out of the bellow, and check for vacuum. If it gets
clogged, or a hose gets pinched, it will cause the cap to cave in, and
burn up the rotor.
Image
1995-96
http://www.summitracing.com/parts/MSD-83811/?rtype=10

http://chevythunder.com/lt1_electrical_page.htm

http://static.summitracing.com/global/i ... m28664.pdf
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: optispark ignition info

Postby grumpyvette » June 9th, 2011, 11:38 am

BUY A SHOP MANUAL FOR YOUR CAR AND GET A FUEL PRESSURE TEST GAUGE AND A V.O.M. METER YOULL NEED THEN ALL
obviously youll need to verify youve got fuel flow and pressure in the fuel rails before worrying about ignition issues

http://members.shaw.ca/corvette86/FuelS ... gnosis.pdf

http://members.shaw.ca/corvette86/Compo ... w%2086.pdf

viewtopic.php?f=32&t=1773

viewtopic.php?f=80&t=728

When you start an L-98 engine Corvette, a series of events take place that causes the engine to run. Knowing the sequence will help you troubleshoot no start conditions.
Fuel Rail Pressurization:
When you first turn the key to the “on” position, the fuel pump will run for 2 seconds pressurizing the fuel rails. There is a Shraeder valve on the passenger side fuel rail near the rear of the engine and if you measure the pressure there after the pump runs, you should see between 40-42 pounds of pressure. The reading will go to 38-40 pounds nominal once the engine is running.test by attaching a fuel pressure gauge to the fuel rail at the shrader valve, on TPI and LT1 engines its located on the pass side fuel rail
Initial Crank Action:
If you then rotate the key to the start position (assuming the anti-theft system has not disabled the starter), the engine will rotate.
Once the oil pressure has reached 4 PSI, the oil pressure switch will close allowing the fuel pump to run. (Note that you should have a black oil pressure switch/sender. It is mounted behind the distributor on the driver’s side and if it is not black, it is suspect due to a run of bad units that stayed in the GM parts pipeline for some time).
The distributor will send a string of pulses to the ECM (Engine Control Module) in response to the engine being rotated by the starter. These pulses continue as long as the engine turns (both starting and running) and if they are not present, the engine will not run.
ECM Reaction:
If the ECM sees oil pressure greater than 4 PSI and the reference pulses from the distributor, it will energize the injector drivers which will begin pulsing the injectors on for 4 ms (milliseconds) periods. (In the L98, all injectors on one side of the engine fire at the same time followed by all injectors on the other side firing at the same time. On the LT-1, the injectors are fired individually at the appropriate time).
The ECM will also pull in the fuel pump relay in effect paralleling it electrically with the oil pressure switch. (If the fuel pump relay fails, you can still normally get the car to start and run unless you can’t make at least 4 PSI oil pressure. This is a “limp home mode” feature put in place to allow for a fuel pump relay failure).
The ECM also monitors the TPS (Throttle Position Sensor mounted on the throttle body assembly) and wants to see .54 volts at this time. If it sees appreciably more than 0.54 volts, it will assume the engine is flooded and the driver has pressed the accelerator to the floor to clear the flooded condition and restrict the fuel flow as a result. (.54 volts during start and at idle from the TPS is very important to both starting and run performance.)
Assuming the ignition module is good (meaning there is a spark of sufficient intensity to ignite the fuel), the engine will “catch”.
Engine "Catches":
When the engine catches, the MAF (Mass Air Flow sensor mounted just ahead of the throttle body) sends a signal to the ECM advising that air is flowing and also just how much air is being pulled through to the intake manifold. The ECM takes note of the amount of air being consumed and adjusts the injector pulse width to around 2.2 ms nominally so as to attain a proper air/fuel mixture to insure combustion. (This is how the 1985 through 1989 L-98 works. For information on the 1990 and 1991 L-98 variant, see the Note below).
The engine should show an initial idle speed of around 900-1100 RPM and then slowly diminish to 600-700 RPM unless the air conditioner is on in which case it will run at around 800 RPM.
If this does not happen, the Idle Air Mixture valve (located on the throttle body) may be misadjusted. Alternatively, there may be a leak in the intake manifold or another vacuum leak may be present. Listen for hissing sounds---there should be none.
ECM Mode:
The engine will now be in Open Loop mode meaning that the ECM is controlling the air/fuel mixture by referencing values stored in memory.
Once the Oxygen sensor (mounted on the exhaust pipe) reaches operating temperature of several hundred degrees, the Manifold Air Temperature (MAT) sensor shows an intake air temperature of more than 140 degrees and the Engine Coolant Temperature (ECT) has reached 160 degrees, the computer will switch to closed loop mode meaning the Oxygen sensor’s output is examined along with the MAT and ECT outputs and the ECM adjusts the injector pulse widths (more “on time” or less “on time”) to constantly strive for a 14.7:1 air/fuel mixture which is the best mixture to hold down pollution.
Note that prolonged idling can force the computer back into open loop mode.
Note: In 1990, the MAF was eliminated from the engine in favor of a speed/density system. This system uses a sensor called the MAP sensor which measures the Manifold Absolute Pressure (hence the name MAP) and compares it with the atmospheric pressure outside the intake manifold. This information, coupled with the Manifold Air Temperature, Engine Coolant Temperature and Engine RPM is used by the ECM to determine the amount of air entering the cylinders. It is a different way of reaching the desired 14.7:1 air-fuel mixture ratio but functionally is like the MAF system in that the ECM uses the feedback to control the "on time" for the injectors.
Corvette used this approach in the 1990 and 1991 L-98 engines and in the 1992 and 1993 LT-1 engines. With the 1994 model C4, they went back to the MAF system. Note that MAF based systems are far more accurate since they measure air flow directly whereas the MAP system infers air flow indirectly. A multitude of things can throw the calculation off and Corvette returned to the MAF system beginning with the 1994 C4 (with a MAP backup). From a troubleshooting standpoint, the MAP operation comes into the sequence the same place that the MAF does.
Summary:
If you have a no start condition or if the L-98 starts and then dies, check the above items in sequence to see if all the events are occurring as required.
A Scan Tool makes this job much easier and is a highly recommended troubleshooting aid for these sorts of problems.

http://www.harborfreight.com/cpi/cta...emnumber=46030
Most of the C4 Corvettes used a MAF (Mass Air Flow) sensor to determine how much air is being pulled into the intake manifold. The exceptions are the 1984 Corvette that used a speed density system--a sort of predictive method of measurement---and the 1990 through 1993 C4 models which were also speed density based. In 1994, Corvette went back to the MAF based system but used the speed density approach as a back up. (1989 Bosch MAF installation shown at right).
A Mass Air Flow sensor has an extremely fine wire inside its bore. The 1985 through 1989 C4 engines used a Bosch MAF sensor that heated the wire to 100 C. The 1994 and later C4 models used a AC/Delco MAF that heated the wire to 200 C. The amount of current required to reach the temperature is measured in each case. (Note: the LT-5 engine used in the ZR-1 used a speed density system and continued to use that system in 1994 and 1995 since the engines had already been made prior to the last two years of production. The ZR-1 therefore has no MAF even after Corvette went back to the MAF based system).
Theory of Operation
As the air travels past the heated wire enroute to the intake manifold, it will cool the wire and additional current is added to again heat the wire to the design temperature. Since the amount of air moving past the sensor is directly related to the amount of cooling experienced by the heated wire, a feedback condition is established whereby the exact amount of moving air is directly related to the amount of current passing through the wire and the intake air is therefore precisely measured.
Once the amount of air is known, the computer controlling the engine can add or subtract fuel as required to maintain the magic 14.7:1 air-fuel mixture resulting in the cleanest burn possible from an emissions (pollution) standpoint.
It does this by varying the "on time" of the fuel injectors. The injectors are pulsed on and off and the width of the pulse is lengthened or shortened as required. When you first start a typical engine, the pulse width is around 4 milliseconds but as soon as the engine "catches" the pulse width is shortened to about 2.2 milliseconds for idle. During operation, the measured air flow through the MAF will cause the computer to increase or decrease the pulse width as explained above.
MAF Operating Conditions
The Bosch MAF is more complex than the AC/Delco version. Both measure the air flow but the Bosch MAF has a circuit called the 'burn-off circuit' that cycles on for about 2 seconds when you shut the engine down. This circuit heats the wire to a high enough temperature to burn off any residue that may have collected on the wire during operation. If you are in a quiet area, you can hear the relays click on and then off on a 1985-1989 C4 as the burn-off cycle occurs.
There are two relays involved with the Bosch MAF: A power relay that passes current to the MAF wire during normal operation and the burn-off relay that provides the current for the cleaning cycle. Both are located on the firewall in the engine compartment, just behind the battery on the drivers side. Bad MAF power and burn-off relays can cause hard starting problems and should be changed periodically as preventative measure and any time you experience hard starting conditions.
The AC/Delco MAF has a power relay but no burn-off relay. For this reason, you should pay even closer attention to the condition of your air filter on a later model C4 than normal since a contaminated wire in a AC/Delco MAF is going to stay contaminated for the most part and cause false signals to be passed to the computer.
Also, the Bosch MAF outputs its information as a analog signal to the computer but the AC/Delco sends its signal as a digital component of varying frequency. For this reason, you cannot measure it's operation directly.
A scan tool is generally the best way to troubleshoot engine problems and with the 1994 and later Corvette, it is virtually mandatory. (An oscilloscope will also work on the AC/Delco MAF but a regular test meter will not).
MAF Problems
Faulty MAF sensors will normally light the check engine light on the drivers information center if the problem is constant and store a trouble code. If intermittent, a trouble code will still be stored as long as the battery is not disconnected.
Normally, the problem is a poor connection at the sensor and wiggling the wires, unplugging and reinserting the connector will often cure the problem.
A faulty MAF will normally cause a no start or difficult start condition and although you can eventually get the car into the "limp-home" mode in most cases, you need to attend to the problem ASAP.
this flow chart might help
http://members.shaw.ca/corvette86/Fu...mDiagnosis.pdf
AC/Delco sensors can become intermittent or give false readings if the wires become contaminated as explained above.
The MAF is a critical part of the emission control system and as such will cause the computer to react to problems very quickly, setting trouble codes and reducing performance in ways that cannot be ignored for long.
MAF Mods
The Bosch MAF is often modified by removing the two screens that are present in the front and rear of the cylinder. Removing these screens significantly increases the air flow through them and this results in more horsepower. Removing the screens is an old trick from the Corvette Challenge days in 1988 and 1989. It does work but is illegal in many states so be advised not to do anything that will get you arrested for a pollution violation.
The AC/Delco MAF is not readily modified. It is what it is but since it is a larger diameter than the Bosch, it responds well to changing the air filter to a free flowing type such as the K&N filter.
Welcome to C4 vette codes it is very ....repeat very
important that if you are not savvy of working on your
vette ...you would be better off - taking your car to a
dealership for repairs on your trouble codes.
However if you feel that you want to dive right in ..than you
have come to the right place.First locate your car's alcl
this component is located just below the instrument panel and
to the left of the center console. Remove the plastic cover
the first two slots to your right are the A & B slots for a drawing of
the alcl module's picture is added below.
The A slot is the diagnostic slot and the B slot is the ground
slot. insert the computer key into these slots (with the engine
off) this is very important...now only put the ignition key
to on ( not start !!!) the check engine light will display a
code 12 which is one flash followed by two flashes.
this code will be flashed three times ..followed by the
trouble code stored in your car's computer.
what ever the code is it will be flashed three times.
have a paper and pencil ready and write down the
code .
code 13 =1 flash followed by 3 flashes =>oxygen sensor
code 14 =1 flash followed by 4 flashes =>coolant sensor
code 15 =1 flash followed by 5 flashes =>coolant sensor
code 21 = 2 flashes followed by 1 flash =>throttle position sensor
code 22 = 2 flashes followed by 2 flashes=> throttle position sensor
code 23 = 2 flashes followed by 3 flashes=> manifold air temp sensor
code 24 = 2 flashes followed by 4 flashes=> vehicle speed sensor
code 25 = 2 flashes followed by 5 flashes=> manifold air temp sensor
code 32 =>egr system
code 33 =>map sensor
code 34 =>maf sensor
code 35 => idle air control
code 41 => cylinder select error
code 42 => electronic spark control
code 43 => electronic spark control
code 44 => lean exhaust
code 45 => rich exhaust
code 51 => PROM
code 52 => fuel calpak
code 53 => system over voltage
code 54 => fuel pump circuit
code 55 => ecm
code 62 => oil temp
please remember that if you have the computer key installed
in the alcl and you start the engine ( you will ruin the engine's computer
)
only put the ignition to on (not to start)
If you should get a check engine soon display.. you can use
the above procedure and codes to buy the right part
or at the very least to keep from getting taken for a ride
and be made to pay hight prices for some inexpensive
module that you could have installed yourself.
You never ask a barber if you need a haircut ..
so you have to be on guard they will see you comming
a mile away.
If your engine displays a trouble code ... your engine will
go into limp mode ..it will still run but very poorly.
you might be able to reset the computer if it will not start
( just to get home ) by disconnecting both battery cables
and re-installing them ...this is not recommended ..but if
you are stranded it might help unitl you get your car home
or to a repair shop..good luck
1985 TO 1991:

Code #12: Normal No Codes.
Code #13: Open Oxygen Sensor Circuit.
Code #14: Coolant Sensor Circuit Low.
Code #15: Coolant Sensor Circuit High.
Code #21: Throttle Position Sensor High.
Code #22: Throttle Position Sensor Low.
Code #23: Manifold Air Temperature Circuit High.
Code #24: Vehicle Speed Sensor.
Code #25: Manifold Air Temperature Circuit Low.
Code #32: EGR System Failure.
Code #33: Mass Air Flow Sensor High.
Code #34: Mass Air Flow Sensor Low.
Code #36: Mas Air Flow Sensor Burn-Off Function Fault.
Code #41: Cylinder Select Error.
Code #42: Electronic Spark Timing.
Code #43: Electronic Spark Control.
Code #44: Lean Exhaust indication.
Code #45: Rich Exhaust Indication.
Code #46: Vehicle Anti Theft Fault.
Code #51: Faulty Mem-Cal.
Code #52: Fuel Calpak Missing.
Code #52(1990-91 Corvette Only): Engine Oil Temperature Sensor Low.
Code #53: System Over Voltage.
Code #54: Fuel Pump Circuit Low Voltage.
Code #55: Defective ECM.
Code #62: Engine Oil Temperature Sensor Circuit High.

ECM CODES 1992 TO 1993:

Code #12: Normal No Codes.
Code #13: Left Oxygen Sensor Circuit.
Code #14: Coolant Temperature Sensor Circuit High.
Code #15: Coolant Temperature Sensor Circuit Low.
Code #16: Opti-Spark Ignition Timing System.( Low Pulse)
Code #21: Throttle Position Sensor Circuit High.
Code #22: Throttle Position Sensor Circuit Low.
Code #23: Intake Air Temperature Sensor Circuit Low.
Code #24: Vehicle Speed Sensor Circuit.
Code #25: Intake Temperature Sensor Circuit High.
Code #26: Quad-Driver Module #1 Circuit.
Code #27: Quad-Driver Module #2 Circuit.
Code #28: Quad-Driver Module #3 Circuit.
Code #32: Exhaust Gas Recirclation Circuit.
Code #33: Manifold Absolute Pressure Sensor Circuit Low.
Code #34: Manifold Absolute Pressure Sensor Circuit High.
Code #36: Opti-Spark Ignition Timing System. (High Resolution Pulse.)
Code #41: Electronic Spark Timing Circuit Open.
Code #42: Electronic Spark Timing Circuit Grounded.
Code# 43: Electronic Spark Control Circuit.
Code #44: Left Oxygen Sensor Circuit Lean.
Code #45: Left Oxygen Sensor Circuit Rich.
Code #51: Mem-Cal Error.
Code #52: Engine Oil Temperature Sensor Circuit Low.
Code #53: System Voltage.
Code #55: Fuel Lean Monitor.
Code #56: Vacuum Sensor Circuit.
Code #61: Secondary Port Throttle Valve System.
Code #62: Engine Oil Temperature Sensor Circuit High.
Code #63: Right Oxygen Sensor Circuit Open.
Code #64: Right Oxygen Sensor Circuit Lean.
Code #65: Right Oxygen Sensor Circuit Rich.
Code #66: A/C Pressure Sensor Circuit Open.
Code #67: A/C Pressure Sensor Circuit. (Sensor or A/C Clutch Circuit Problem)
Code #68: A/C Relay Circuit Shorted.
Code #69: A/C Clutch Circuit.
Code #72: Gear Selector Switch Circuit.



CODES 1994 TO 1996:

DTC #11: Malfunction Indicator Lamp Circuit.
DTC #13: Bank #1 Heated Oxygen Sensor #1 Circuit:
DTC #14: Engine Coolant Temperature Sensor Circuit Voltage Low.
DTC #15: Engine Coolant Temperature Sensor Circuit Voltage High.
DTC #16: Distributor Ignition System Low Pulse.
DTC #18: Injector Circuit.
DTC #21: Throttle Position Sensor Circuit Voltage High.
DTC #22: Throttle Position Sensor Circuit Voltage Low.
DTC #23: Intake Temperature Sensor Circuit Voltage High.
DTC #24: Vehicle Speed Sensor Circuit.
DTC #25: Intake Air Temperature Sensor Circuit Voltage Low.
DTC #26: Evaporative Emission Canister Purge Solenoid Valve Circuit.
DTC #27: EGR Vacuum Control Signal Solenoid Valve Circuit.
DTC #28: Transmission Range Pressure Switch Assembly Fault.
DTC #29: Secondary Air Injection Pump Circuit.
DTC #32: Exhaust Gas Recalculation.
DTC #33: Manifold Absolute Pressure Sensor Circuit High.
DTC #34: Manifold Absolute Pressure Sensor Circuit Low.
DTC #36: Distributor Ignition System High Pulse.
DTC #37: Brake Switch Stuck On.
DTC #38: Brake Switch Stuck Off.
DTC #41: Ignition Control Circuit Open.
DTC #42: Ignition Control Circuit Shorted.
DTC #43: Knock Sensor Circuit.
DTC #44: Bank 1 LF Heated Oxygen Sensor #1 Circuit Lean.
DTC #45: Bank 1 LF Heated Oxygen Sensor #1 Circuit Rich.
DTC #47: Knock Sensor Circuit Or Module Missing.
DTC #48: Mass Air Flow Sensor Circuit.
DTC #50: System Voltage Low.
DTC #51: EEPROM Programming Error.
DTC #52: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #53: System Voltage Low.
DTC #55: Fuel Lean Monitor.
DTC #58: Transmission Fluid Temperature Sensor Circuit Low.
DTC #59: Transmission Fluid Temperature Sensor Circuit High.
DTC #62: Engine Oil Temperature Sensor Circuit Voltage Low.
DTC #63: Bank 2 RF Heated Oxygen Sensor #1 Circuit Open.
DTC #64: Bank 2 RF Heated Oxygen Sensor #1 Circuit Lean.
DTC #65: Bank 2 RF Heated Oxygen Sensor #1 Circuit Rich.
DTC #66: A/C Refrigerant Pressure Sensor Circuit Open.
DTC #67: A/C Pressure Sensor Circuit Sensor or A/C Clutch.
DTC #68: A/C Relay Circuit.
DTC #69: A /C Clutch Circuit.
DTC #70: A/C Clutch Relay Driver Circuit.
DTC #72: Vehicle Speed Sensor Loss.
DTC #73: Pressure Control Solenoid Circuit Current Error.
DTC #74: Traction Control System Circuit Low.
DTC #75: Transmission System Voltage Low
DTC #77: Primary Cooling Fan Relay Control Circuit.
DTC #78: Secondary Cooling Fan Relay Control Circuit.
DTC #79: Transmission Fluid Overtemp.
DTC #80: Transmission Component Slipping.
DTC #81: Transmission 2-3 Shift Solenoid Circuit.
DTC #82: Transmission 1-2 Shift Solenoid Circuit.
DTC #83: Torque Converter Solenoid Voltage High.
DTC #84: 3-2 Control Solenoid Circuit.(Auto Only).
DTC #84: 2nd And 3rd Gear Blockout Relay Control Circuit.
DTC #85: Transmission TCC Stock On.
DTC #90: Transmission TCC Solenoid Circuit.
DTC #91: One To Four Upshift Lamp(Manual Only).
DTC #97: VSS Output Circuit.
DTC #98: Tachometer Output Signal Voltage Wrong.
_________________you really can,t be effectively at playing mr-fix-it with out the correct tools
especially on the more modern cars that are computer controlled, the days of effectively tuning by ear and vacuum gauge and engine sound went out with carbs
you need a few basic tools, now the list will vary, but you can,t get by by guessing, you neet to know and test now that sensors and CPUs control engine function



This is from http://shbox.com/
A fuel pressure test gauge can be bought at your local auto supply for ~$35. Attach it to the schrader valve that is on the fuel rail. Schrader valve location on 1994-1997
Normal pressure when the engine is not running and lines have been pressurized is 41-47 psi. This same pressure should be observed at wide open throttle (WOT). WOT can be simulated by removing the vacuum hose to the regulator at idle. At idle (because of the effect of the vacuum to the regulator) pressure will be less than what you observe with the vacuum line off. There may be anything from a 3 to 10 psi difference. NOTE: any indication of fuel in the vacuum line to the regulator, means the regulator is leaking and should be replaced. Check the line for fuel or the smell of fuel.
To fully determine that you don't have a pressure drop off during actual WOT situations, you should tape the gauge to your windshield and take it for a test run. This will tell you if the pump can meet actual fuel flow demands at pressure and not just at a simulated WOT condition (as when removing the vacuum to the regulator).
When you have a gauge connected and the pressure looks initially good and then bleeds off quickly when you shut the engine off, you can do a couple of tests to help you figure out where the pressure loss is.
What the factory manual says to temporarily install, is a set of "fuel line shut off adapters" (probably something the normal guy is not going to have available). You remove the fuel lines from the rail and connect these valves in between. This lets you shut off either side of the lines for testing.
You can do the same thing by pinching the flexible lines to shut them off, but risk breaking them. You might be able to do it (your risk) by using a needle nose vise grips and putting some scrap hose as cushions on the jaws. Then use that to clamp off the line just enough to seal it. Obviously, this is not the best way to shut off the lines and could result in breakage. Heat and age can make the hoses brittle. If you don't want to risk it, don't. It's just a suggestion.
You can use the fuel pump prime connector for pressurizing the system (jumper 12v to it to run the pump).
Watch your gauge as you jumper the prime connector. When you have good pressure remove the jumper and clamp off (or use shut off valve) the fuel supply line (3/8 pipe). If pressure holds, you have a leak on the feed line somewhere before it gets to the clamp (or shut off valve) or at the check ball in the pump. If it still goes down, release your clamp (or open shut off valve). Pressurize the system again, then remove the jumper and this time clamp (or shut off) the return line (5/16 line). If pressure holds, then the regulator is faulty. If pressure does not hold, you need to locate leaky injector(s). If you can't tell a leaky injector from reading the plugs, you can look and see if injectors are leaking by removing the fuel rail screws and pull the rail and all the injectors up, so you can see under them. Leave them over the injector ports. Pressurized the system and look under the injectors to see if any are dripping.
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: optispark ignition info

Postby grumpyvette » July 23rd, 2011, 5:05 pm

http://www.car-stuff.com/1992chevroletc ... sensor.htm

http://www.partstrain.com/ShopByDepartm ... VETTE/1992

http://corvetteactioncenter.com/tech/c4 ... Z1XqJwcC10

http://para.noid.org/~muttvette/opti.html

http://www.partstrain.com/store/details ... 11801.html

viewtopic.php?f=50&t=8136&start=10

if your replacing the opti ignition don,t forget to replace the crank position sensor also as they can also cause problems

Image

Image

Image

Image
ONLY THE 1996 LTI and all the LT5 C4 CORVETTEs CAME FROM THE FACTORY WITH THE CRANK POSITION SENSOR
Image


ONLY THE 1996 LTI and all the LT5 C4 CORVETTEs CAME FROM THE FACTORY WITH THE CRANK POSITION SENSOR
Hope this helps
The crankshaft position sensor provides the PCM with crankshaft speed and crankshaft position. The PCM utilizes this information to determine if an engine Misfire is present. The PCM monitors the CKP sensor for momentarily drop in crankshaft speed to determine if a misfire is occurring. When the PCM detects a misfire, a DTC P0300 will set.

The PCM also monitors the CKP sensor signal circuit for malfunctions. The PCM monitors CKP signal and the High and Low resolution signals. The PCM calculates these signals to determine a ratio. When the PCM detects that the ratio is out of normal operating range, the PCM will set a DTC P0335 or a DTC P0336.


Distributor Ignition (DI) System
The distributor ignition system controls fuel combustion by providing a spark to ignite the compressed air/fuel mixture at the correct time. To provide improved engine performance, fuel economy, and control of exhaust emissions, the PCM controls distributor spark advance (timing) with an Ignition Control (IC) system. Only the IC system will be described here. Additional information on the system is found in Ignition System (6D).
Image

Image
To properly control ignition/combustion timing the PCM needs to know:

Camshaft position.
Engine speed (RPM).
Engine load (manifold pressure or vacuum).
Atmospheric (barometric) pressure.
Engine coolant temperature.
The amount of detonation.
Distributor Ignition System




(1) Ignition Coil Wire
(2) Ignition Coil Module
(3) Ignition Coil
(4) Distributor

The distributor ignition system is a net build distributor (no timing adjustment) that provides angle based timing information to the PCM for individual cylinder spark timing. The ignition module is capable of providing both 4X and 180X timing pulses each crankshaft revolution. Using these timing pulses, the PCM processes ignition spark timing and sends an IC signal to the ignition coil module to activate the secondary ignition system.

The PCM provides the distributor with the following:

Ignition voltage circuit.
Ground circuit.
Two 5 volt reference voltages to the ignition control module.
As the camshaft turns (during crank or run), a slotted two-track timing disk is rotated inside the ignition control module. Each time a slot in either track of the disk is properly aligned, the ignition control module will pulse one of the 5 volt reference voltages to ground. A reference signal is generated each time the PCM detects that the reference voltages have been grounded by the ignition control module. When the PCM detects reference signals, ignition timing can be processed.

The PCM will also compare the 4X and the 180X signals to each other to determine the location of the number one cylinder and top dead center. In addition, if only one signal is being received by the PCM a Diagnostic Trouble Code (DTC) will be set. DTC P1371 will be set if the 4X signal is missing and DTC P0372 will be set if the 180X signal is missing. The vehicle will not run if the 4X (Reference) signal is not available at the PCM for processing.

The Ignition Control (IC) system consists of the following:

• Camshaft Position Sensor

• Ignition Coil

• Ignition Coil Module

• Powertrain Control Module.

These circuits perform the following functions:

• Low resolution signal reference.

- This provides the PCM with reference signals, firing order, and camshaft position information. If the low resolution signal circuit becomes open or grounded, the engine will not run because the PCM will not operate the ignition coil module, fuel pump, or the fuel injectors.

- A DTC P1371 will set if the PCM receives high resolution signal references without the low resolution signals.

• High resolution signal reference.

- This provides the PCM with detailed reference signals and crankshaft position information.

- If this circuit becomes opens or grounded a DTC P0372 will set and the engine will still run.

- When there is a malfunction with the high resolution circuit, excessive crank times will be experienced.

• System ground.

- This circuit is grounded at the PCM and provides ground for the distributor to generate low and high resolution signal reference signals.

- If this circuit becomes open, the engine will not run since there will be no reference information.

• Ignition Control (IC).

- This circuit controls the ignition coil ON and OFF time. It signals the ignition coil module to begin primary coil dwell current when the IC is high. The ignition coil module shuts OFF ignition coil current when the signal goes low.

- If this circuit becomes open, shorted to voltage, or grounded, the engine will not start and a DTC P1351 or P1361 will set.

FIGURE Ignition Wire Harness Assembly Routing(c)




(1) Cylinder #1
(2) Cylinder #2
(3) Cylinder #3
(4) Cylinder #4
(5) Cylinder #5
(6) Cylinder #6
(7) Cylinder #7
(8) Cylinder #8
(9) Distributor Assembly

Results of Incorrect Operation
An open IC circuit will set a DTC P1351. A grounded IC circuit will set a DTC P1361. An open or grounded IC circuit will result in an engine cranks but will not run. An open or ground in the low resolution signal circuit will set a DTC P1371 and the engine will not start. If the high resolution signal circuit becomes open or grounded a DTC P0372 would set. This will cause reduced performance and poor fuel economy.

An inoperative distributor vent system may cause premature distributor failure.

The PCM uses information from the MAP and engine coolant temperature sensor in addition to RPM to calculate spark advance as follows:

• Cold engine = More spark advance.

• Engine under minimum load based on RPM and low amount of air flow - More spark advance.

• Hot engine = Less spark advance.

• Engine under heavy load based on RPM and high amount of air flow - Less spark advance.

For removal and replacement of ignition system components, refer to Section 6D4, Ignition System.

The description, operation and repair procedures of the distributor ignition system components are found in Service Category Ignition Systems. For misfire or ignition control check, refer to the following DTCs:

P0300
P0323
P0372
P1351
P1361
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
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Re: optispark ignition info

Postby Randy_W » July 23rd, 2011, 7:15 pm

The B-bodies, Impala SS, Buick and Caddy always had a vented Opti from day one in the 1994 models, if you have a choice always get the vented unit. I have well over 100k miles on used vented Optispark units and never had a hiccup.
Randy
Don't mess with old men, we didn't get that way by being stupid!
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Re: optispark ignition info

Postby grumpyvette » December 27th, 2013, 5:12 pm

1963SS wrote:Most likely it's Opti related. I personally like the Opti and have never had a failure either on my 1995 mpala or my 1995 Vette. They are really durable. With that said......there are a few steps you can do with a voltmeter if you have the skillz. Here is an article that I've used to troubleshoot Opti or harness related problems. Sometimes it's as simple as reseating the Opti extension harness, other times, not so much.

Here's everything you'll need to check the Opti. Shouldn't take over 20-30 minutes.

The opti has two functions in the spark process. The first thing that happens is as the cam turns, the optical section of the optispark picks up the signals by the rotation of the shutter wheel. The pulses are sent to the PCM via the optispark electrical harness. The PCM processes the signals along with other sensor input and determines the proper time for the coil to fire. The PCM sends a signal to the Ignition Control Module (ICM) and it, in turn, causes the coil to fire. The spark from the coil travels through the coil wire back to the secondary ignition section of the optispark (cap and rotor), to be distributed to the proper cylinder.

If the opti is never sending the signal to the PCM, the PCM will never send a signal to fire the coil. The PCM will also not generate any injector pulses.

Here is some testing you can do. Refer to this diagram for 94-95s. 93 and 96-97 ignition system diagrams are slightly different overall, but the ICM connector is the same. Note: Pay attention to the fact that the diagram may show A-B-C-D out of order for ease of diagramming. They are actually in proper order on the physical connector. The connector has the letters embossed on it, so make sure you are testing the correct one.

Image

Image

Disconnect the ICM connector. Leave coil connected (important).

Turn key to ON.

Check for dc voltage with a digital meter at harness terminal "A" to ground and and also "D" to ground. Note: Use a modern digital meter with at least 10 megohm impedance to protect the PCM (in case you measure anything in that direction). Do not use a test light for looking at voltage potentials from electronics! Also make sure your meter leads make good contact and are clean and tight. Check that you get a zero ohms reading by touching the two leads together. If it is not zero, merely adjust the readings you take by the skew. That will ensure accurate resistance readings.

Result should be 10v dc or more on the A and D terminals. If you get no voltage, use the diagram and chase back toward the coil and the ignition fuse. Power for the ICM comes from the ignition fuse and through the coil, so any of that could be bad.
If you have good voltage, switch the meter to ac scale and connect test leads to terminal "B" and to ground. Observe meter while cranking the engine. You should see between 1 and 4 volts ac (those are the pulses that trigger the coil to fire).

If you don't see the proper ac voltage the problem could be the optispark, the harness to the optispark, the PCM (not common) or any of the wiring in between. Visually inspect all the connections for possible poor contact or corrosion.

You should also check "C" of the ICM harness for continuity to ground.

ICM Harness

A = ~10vdc-12vdc (or your system voltage)
B = 1vac-4vac while cranking
C = ~ 50 ohms or less with key ON ..... ~ 0 ohms to ground with key OFF
D = ~10vdc-12vdc (or your system voltage-might be slightly less than reading at "A")


At the end of the optispark harness (disconnected from the opti) with the key ON, you should see:

Optispark Harness

A = ~5vdc
B = ~5vdc
C = ~12vdc (or your system voltage)
D = ~60 ohms with key ON ..... ~0 - 0.2 ohms ground with key OFF
IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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Re: optispark ignition info

Postby grumpyvette » December 22nd, 2014, 10:38 am

1963SS wrote:Here's a test sequence that I use for checking for a no start condition. The ECM has got to see the signal from the Opti or there will be no pulses above or below 300 RPM.

Pay attention to where the instructions say to use an AC or DC scale on your meter. We are using the AC scale because rapidly pulsating DC will appear as AC to a meter. It's not as accurate as an oscope but it does work well.

Here's the theory of operation and the test sequence. Take the reading and holler back if you have any questions. This will fix any Opti related problems in a few minutes.

It's the same procedure for all years Opti. First, do you have any codes and then do this.

Trouble codes 16, P0323 for low resolution or 32, P0372 for high resolution may lead you to this procedure. Though, note that the low resolution code does not cause the Check Engine light to come on. So, you may have opti troubles without a light on the dash. A hard low resolution signal failure will not allow engine operation (no spark, no fuel injector pulses, no fuel pump operation [except prime]). Intermittent low resolution failure will consequently cause intermittent engine operation or stumbling. High resolution codes do cause the light to come on and engine will often continue to run (but maybe not as it should at all times).

The opti has two functions in the spark process. The first thing that happens is as the cam turns, the optical section of the optispark picks up the signals by the rotation of the shutter wheel. The pulses are sent to the PCM via the optispark electrical harness. The PCM processes the signals along with other sensor input and determines the proper time for the coil to fire. The PCM sends a signal to the Ignition Control Module (ICM) and it, in turn, causes the coil to fire. The spark from the coil travels through the coil wire back to the secondary ignition section of the optispark (cap and rotor), to be distributed to the proper cylinder.

Remember, if the opti is never sending the signal to the PCM, the PCM will never send a signal to fire the coil or generate any injector pulses.

Here is some testing you can do. Refer to this diagram for 94-95s. 93 and 96-97 ignition system diagrams are slightly different overall, but the ICM connector is the same. Note: Pay attention to the fact that the diagram may show A-B-C-D out of order for ease of diagramming. They are actually in proper order on the physical connector. The connector has the letters embossed on it, so make sure you are testing the correct one.

Disconnect the ICM connector. Leave coil connected (important).

Turn key to ON.

Check for dc voltage with a digital meter at harness terminal "A" to ground and and also "D" to ground. Note: Use a modern digital meter with at least 10 megohm impedance to protect the PCM (in case you measure anything in that direction). Do not use a test light for looking at voltage potentials from electronics! Also make sure your meter leads make good contact and are clean and tight. Check that you get a zero ohms reading by touching the two leads together. If it is not zero, merely adjust the readings you take by the skew. That will ensure accurate resistance readings.

Result should be 10v dc or more on the A and D terminals. If you get no voltage, use the diagram and chase back toward the coil and the ignition fuse. Power for the ICM comes from the ignition fuse and through the coil, so any of that could be bad.
If you have good voltage, switch the meter to ac scale and connect test leads to terminal "B" and to ground. Observe meter while cranking the engine. You should see between 1 and 4 volts ac (those are the pulses that trigger the coil to fire).

If you don't see the proper ac voltage the problem could be the optispark, the harness to the optispark, the PCM (not common) or any of the wiring in between. Visually inspect all the connections for possible poor contact or corrosion.

You should also check "C" of the ICM harness for continuity to ground.

ICM Harness

A = ~10vdc-12vdc (or your system voltage)
B = 1vac-4vac while cranking
C = ~ 50 ohms or less with key ON ..... ~ 0 ohms to ground with key OFF
D = ~10vdc-12vdc (or your system voltage-might be slightly less than reading at "A")


At the end of the optispark harness (disconnected from the opti) with the key ON, you should see:

Optispark Harness

A = ~5vdc
B = ~5vdc
C = ~12vdc (or your system voltage)
D = ~60 ohms with key ON ..... ~0 - 0.2 ohms ground with key OFF

IF YOU CAN,T SMOKE THE TIRES AT WILL,FROM A 60 MPH ROLLING START YOUR ENGINE NEEDS MORE WORK!!"!
IF YOU CAN , YOU NEED BETTER TIRES AND YOUR SUSPENSION NEEDS MORE WORK!!
grumpyvette

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