adjusting your TPS AND IAC



adjusting your TPS AND IAC

Postby grumpyvette » September 19th, 2008, 5:07 pm

yes IM well aware theres a great deal of links with info you need to read that you'll most likely skip over,..... when you find you've got questions or just want to fully understand the process reading the links provides you with the required info, so ID strongly suggest taking the time to read thru them, as you'll be amazed at what they contain.
the prime symptoms of a defective IAC is an engine that either won,t idle at a consistent RPM,or it won,t keep running, or it just changes speeds and won,t settle down almost like a vacume leak, a defective or badly adjusted or defective TPS tends to result in a loss of engine response and either fouled plugs or plugs showing excessively lean combustion.
the TPS is easily checked with a multi meter, the IAC can be removed and cleaned, as will the throttle body its installed in, but these do go bad and need replacing


Start and run engine until it reaches operating temperature (closed loop)
Check and set ignition timing to 6 degrees before dead center (BDC) with tan EST wire disconnected
Check and set throttle position sensor (TPS) to .54 (+/- .08) volts at idle
Jumper terminals "A" and "B" on the ALDL
Turn ignition key on and do not start engine
Wait 60 seconds so that the idle air control (IAC) motor fully extends
Without turning ignition key off, remove connector from IAC motor
Turn ignition key off and disconnect ALDL jumper
Attach external RPM meter using Tach port or scanner using ALDL port
Start and run engine until it reaches operating temperature (closed loop)
Remove minimum idle air cap using awl if required
Adjust idle speed to 425 (+/- 25) rpm in either in park or neutral
Turn ignition key off and reconnect EST wire and IAC motor
Check and set throttle position sensor (TPS) to .54 (+/- .08) volts at idle
Reset ECM by disconnecting and reconnecting power at battery terminal
Depress accelerator pedal slightly
Start and run engine for 5 seconds
Turn ignition key off for 10 seconds
Drive vehicle to assist in ECM reprogramming
If you used a scanner, you should see around 20 IAC steps

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YES THERE'S SEVERAL SUB LINKS
(IN MOST OF THE THREADS)
THEY ALL CONTAIN A BIT DIFFERENT RELATED INFO YOU'LL NEED

ANYTIME YOUR DEALING WITH THE ENGINE AND HOW IT RUNS ,
YOULL BE DEALING WITH DIFFERENT ISSUES,
COOLANT AND OIL TEMPS,& PRESSURE
FUEL PRESSURE , INJECTOR FUNCTION
FUEL DELIVERY, PRESSURE & VOLUME
RELATED FUEL / AIR RATIO
EFFECTIVE COMPRESSION & RING SEAL
VALVE TIMING & LIFT & DURATION & VALVE SEAL
IGNITION SPARK TIMING & STRENGTH, & IGNITION ADVANCE CURVE
EXHAUST BACK PRESSURE
SENSOR OUTPUT TO THE CPU
VOLTAGE & GROUNDS
http://www.thirdgen.org/tpimod2

http://www.batee.com/corvette/dcrg/read ... s_sim5.htm

viewtopic.php?f=80&t=728&p=1243&hilit=electrical+connectors#p1243

https://www.youtube.com/watch?v=S_ni39iwAys

viewtopic.php?f=32&t=6550&p=20807#p20807

http://www.mamotorworks.com/corvette-c4 ... 6-903.html

http://www.docstoc.com/docs/25331704/Co ... u-1992-Not

viewtopic.php?f=55&t=5307&p=15751&hilit=runners+gaskets+leak#p15751

http://www.iroczone.com/techarttpsadj.html

http://www.haltech.com/product/platinum ... /sport-gm/

http://temp.corvetteforum.net/c4/vader86/tpsiac.html

http://www.golenengineservice.com/html/tps.html

http://www.s-series.org/htm/how2/tpsadjust.htm

viewtopic.php?f=3&t=330&p=5167&hilit=start+sequence#p5167

http://www.jcwhitney.com/autoparts/Sear ... p=ZX503796

http://www.summitracing.com/parts/SUN-CP9001

viewtopic.php?f=44&t=366&p=448#p448

http://www.etoolcart.com/autoxray-scann ... x6000.aspx

viewtopic.php?f=55&t=1475&p=3325#p3325

http://www.corvetteactioncenter.com/kb/ ... Idle+Speed

http://www.thirdgen.org/tpimod1
http://www.ecklerscorvette.com/corvette ... 1991.html#

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1st, the IAC motor is not a sensor, it's an actuator.
2nd, yes, engine can run without it if waiting for a new one.
3rd, ensure the idle speed screw is set to achieve an IAC position of around 5-10 counts at hot idle.
4th, ensure the spark plug wires (or any other high voltage wiring) aren't too close to the IAC motor/wiring.
5th, IAC TEST: When turning off the engine, watch the IAC pintle; it should fully close, then open halfway.



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ONE WAY
IAC and TPS Adjustment
Tom Keliher
Idle Air Control
Tools needed:

Torx bit # T-20
Paper Clip
Small Punch

Take the paper clip and open it up and form it into a big "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' pins.

Turn on the ignition, but don't start the engine. Wait 30 seconds. Now, go remove the connector from the IAC.

Start engine. You are now going to adjust "minimum air". There is a Torx screw on the side of the throttle body. This is what needs to be turned to adjust minimum air, or more commonly known as "idle speed". It comes from the factory with a protective metal cap over it. If the cap is still there, use a small punch to knock it out. Set the idle speed to 450-500 rpm, rotating the Torx screw clockwise to raise rpm, and counter-clockwise to lower rpm. Once the idle rpm is set, turn off the engine.

Re-connect the connector onto the IAC. Start engine. Idle speed is now once again governed by the ECM, but your idle should be smooth and steady, approximately 600 rpm in Drive (for unmodified cars).

If you set an SES light by having the IAC disconnected, then after shutting down the engine disconnect the negative battery terminal. Wait 5 minutes. This will clear the ECM of all trouble codes. Re-connect the battery and drive the car for 20 minutes to allow the ECM to relearn your driving style.

Throttle Position Switch (TPS)
Tools needed:

Digital Volt-Ohm-Meter (VOM)
Jumper Wires (make your own)
Auto Xray Scanner (if available) will eliminate the need for VOM and jumper wires.

Turn on ignition, but don't start the engine.

With a scanner: plug in the scanner and read the TPS voltage. It should be 0.54Volts +/- 0.075Volts

With VOM and jumper wires: disconnect the connector from the TPS. Using your jumper wires, make a connection allowing some room for the VOM terminals to contact the jumper leads and read the TPS voltage.

If out of spec, loosen the two screws holding the TPS to the throttle body, and slightly rotate the TPS up or down, reading the voltage until it comes into specification. Tighten screws. Using the throttle lever, rotate the throttle to WOT (wide open throttle). The TPS voltage should be over 4.0 volts. Close the throttle again, and then slowly open it to WOT, observing the voltage reading. It should increase progressively and in a linear fashion. If it sticks or jumps or falls off at all while doing this check, that could mean a bad TPS switch and could be a cause of stumbling and drive ability problems.

After setting the correct voltage, turn off ignition switch. Remove jumpers/scanner and reconnect the TPS connector as required.

be sure you've checked the ignition timing with a decent timing light


SECOND EXPLANATION


Tools needed:

Torx bits or drivers (T-10, T-15, maybe more depending on the application)
Voltmeter (digital is best, but a really accurate analog will work)
Tachometer (the one in the vehicle will work fine if equipped)
Wrenches and an awl (various sizes, only if the idle speed hasn’t ever been set)

Theory of Operation – (lengthy)

A common myth about fuel injected vehicles is that the idle speed is fixed and cannot be adjusted. This isnt quite true; there is a setting. It's called minimum air, which is adjustable on TBI and MPFI vehicles. This setting sets the lowest-possible idle speed for the vehicle. The ECM uses the IAC (idle air controller) to raise the idle speed from this adjustment. So, while the exact idle speed isn’t really adjustable, the minimum idle speed is.

Why adjust the idle speed? Isnt the ECM supposed to do that? Yes it does and it does do a good job, but has to have a starting point. That starting point is called minimum air, or the smallest amount of air allowed to enter the engine with the throttle closed. The ECM can only add air to that minimum setting. If that setting is too high, the ECM cant slow the engine down to an acceptable idle. If the setting is too low, the ECM may not be able to keep the engine running under certain conditions.

Another reason to adjust minimum air is if there has been some repairs to the fuel system. If the throttle body has been removed (i.e. rebuilt or cleaned) or the TPS (throttle position sensor) has been replaced or otherwise disturbed (i.e. loosened the mounting screws unintentionally -- it happens) then minimum air should be adjusted. Any changes that could affect idle speed or idle quality, like performance upgrades or replacing leaking vacuum lines, should be followed by setting minimum air. If youve got an early year TPI , thats designed to use a 9th cold start injector,check the cold start injector as its a potential problem source if its not working correctly.

This adjustment, once learned, only takes a few minutes. It rarely has to be adjusted, but it takes so little time to check (and adjust, if needed) that there’s no reason not to do so.



Checking & Adjustment Instructions

To establish minimum air, the idle speed must be set first. The idle speed screw is sealed with a cap from the factory. This should be removed by removing the throttle body and using an awl to pry the plug off. If this seems scary, have it done. It’s not difficult but it’s not worth risking damage to the throttle body or human flesh to remove the plug. Once the plug has been removed, reinstall the throttle body.

Assuming the idle speed screw is accessible and the throttle body is installed, jumper pins A&B on the ALDL (Assembly Line Data Link) connector under the dash. Pins A&B are on the upper-right-hand side. These are the same two pins to jumper to read codes from the ECM. Now turn the key on (the Check Engine light should be lit) and leave the key on for at least 30 seconds. The computer will extend the IAC plunger all the way out to allow adjustment of the idle speed.

After the 30 second wait, unplug the IAC (square 4-pin connector on the throttle body) WHILE THE KEY IS STILL ON. This prevents the ECM from adjusting the idle speed while you make your adjustments.

Block the drive wheels, set the emergency brake, and start the engine. Set the idle speed by adjusting the idle speed screw. The engine should be at operating temperature for this. The exact setting is on the emissions label on the radiator shroud, but in general, the idle speed should be about 500 RPM in Drive, 700 in Park / Neutral, or if you have a manual transmission, somewhere between 600-800 RPM. Remember that the truck is running during this adjustment, so stay clear of the fan, and make sure it can’t roll or otherwise be put into gear while this is done.

Once the minimum idle speed is set, turn the engine off, reconnect the IAC, and remove the jumper from the ALDL connector. The TPS minimum voltage must now be set. Turning the idle-speed screw may have moved the TPS idle voltage away from the specification, so it should be adjusted next.

Connect a voltmeter between pins A (usually dark blue) and B (usually black, or black/pink) of the TPS, and turn the key on. Dont start the engine. Loosen the two torx screws holding the TPS in place, but don’t remove them. Rotate the TPS until the voltmeter reads between 0.45 and 0.55 volts, with 0.50 being ideal. Tighten the mounting screws (carefully, they thread into soft aluminum) and re-check the voltage to make sure it’s still within range.

Thats it. After the procedure is done once, its easy to remember and do. I hope this helps.

take it a step at a time,set the fuel pressure at 40psi, check for vacuum leaks, and adjust the IAC and TPS and set the timing at 8 degrees per the manual,then drive it for 30 minutes to let the computer learn the conditions it operates in

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=168

http://forum.grumpysperformance.com/viewtopic.php?f=70&t=875

http://forum.grumpysperformance.com/viewtopic.php?f=50&t=821&p=1212&hilit=propane+leaks#p1212

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=1401

http://forum.grumpysperformance.com/viewtopic.php?f=70&t=1809
WATCH THE VIDEO, READ THE LINKS
http://www.youtube.com/watch?v=9CPqbaSg ... re=related

a propane torch is both safer and easier to use as a method to locate vacuum leaks, and most surging IS related to defective injectors or vacuum leaks
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(DONT LIGHT IT) just SLIGHTLY open the valve so its allowing gas to flow at a low volume,start the engine and let it idle at the lowest speed you can then place the tip of the UNLIT torch at any suspected vacuum leak and listen for the rpms to increase and watch the tachometer, gas flowing into a vacuum leak will increase engine speed.
look for loose or missing vacuum hoses, cracked or broken power brake connections, emissions system hoses that are loose, vacuum connections to the trans or ignition, loose connectors missing or loose bolts cracked hoses missing assessory connections etc.
naturally this only locates leaks to the outside, and its possible for the intake to suck air from the lifter gallery, so that also needs to be checked if everything else seems to be ok.

read this
viewtopic.php?f=44&t=464

http://www.centuryperformance.com/tunin ... g-148.html
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: adjusting your TPS AND IAC

Postby grumpyvette » October 13th, 2008, 8:21 am

the picture link

http://shbox.com/1/iac2.jpg

http://www.thirdgen.org/tpimod2

yeah thats the problem with EFI, your taught the CPU and codes will locate the problems and point to the source, but its not always the case and theres a zillion things that cause problems that the trouble codes and sensors won,t point too!, in fact theres things that the trouble codes indicate as deffective that may not be!

these are your friends
http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2D900010&N=700+115&autoview=sku

http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2D800299&N=700+115&autoview=sku

http://www.rbracing-rsr.com/rsrgauge.htm

http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUM%2DG1059&N=700+%2D114183+115&autoview=sku

http://www.raytek-northamerica.com/admin/file_handler/2ae6092f570efab9e577de9b6820919c/1017348120/80_Bro_1-1501_Rev_H.pdf

http://www.centuryperformance.com/vacuum.asp

http://www.amazon.com/Corvette-Injection-Electronic-Engine-Control/dp/0837608619/ref=sr_1_15/103-3486570-0918205?ie=UTF8&s=books&qid=1181824450&sr=8-15


KNOWING WHAT YOUR DOING IS IMPORTANT, TO GETTING GOOD RESULTS!
no one knows everything about all models and years so it helps to have the correct procedures and info in a handy referace source,now you can get by with a HAYNES or CHILTONS manual, or something similar, but for detailed info, OWNING the CHEVY SHOP MANUAL FOR YOUR SPECIFIC CAR IS ALMOST MANDATORY!
I get asked frequently, "how did you know how to do that?"
well, EXPERIANCE plays a big roll, working on similar cars and engines helps, and the INTERNET is a good resource... but theres ALWAYS a big need for DETAILED REFERANCE MATERIAL, SPECIFICALLY MATCHING YOUR PARTICULAR CAR and if you have not yet invested in a SHOP MANUAL for the year make and model of you pride and joy muscle car your either not serious about your hobby, or most likely NOT A SERIOUS HOT RODDER! I constantly see guys SCREWING up installations, or adjustments,if you don,t know exactly what your doing, you need to either let the dealer do it and PRAY his mechanics are experianced and can read, OR..if your like ME, you would rather do it yourself and KNOW its been done correctly...
if your not aware, heres where to order them....

1-800-782-4356

http://helminc.com/helm/homepage.asp?r=

your average shop manual may cost $100-$150 ONCE! but youll easily save far more than that in reduced time and screw ups in under a years time or in many cases on one job vs having the dealer do the work!

and yes old brittle electrical connectors can break, so they may need to be replaced, and while the search feature, is always an option here, on this site,
too save time , look at the sub links in these threads, for links to connectors for repair work


viewtopic.php?f=36&t=3105&p=8272&hilit=connectors+pigtails#p8272

viewtopic.php?f=32&t=168&p=41767&hilit=connectors+pigtails#p41767
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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Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: adjusting your TPS AND IAC

Postby grumpyvette » December 25th, 2008, 5:53 pm

other mods


http://www.ws6.com/mycar.htm

http://www.eecis.udel.edu/~davis/z28/ecm_swap/

http://www.thirdgen.org/newdesign/tech/tpimod1.shtml

http://www.thirdgen.org/newdesign/tech/ ... pass.shtml

http://www.thirdgen.org/newdesign/tech/ednitrous.shtml

http://store.summitracing.com/default.a ... &x=23&y=12

1985 vacuum line diagram
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Image

http://www.thirdgen.org/tpimod2

the above info should help, but get a SHOP MANUAL,TIMING LIGHT,VACUUM GAUGE,V.O.M. METER, YOULL NEED THEM,

READ THIS SUB LINK
viewtopic.php?f=32&t=168

http://www.eficonnection.com/eficonnection/default.aspx

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How to Adjust your Early C4 TPS and Idle Speed -- 1 of 1


Submitter's Name: Lars Grimsrud


How to Adjust your Early C4 TPS and Idle Speed by Lars Grimsrud SVE Automotive Restoration Musclecar, Collector & Exotic Auto Repair & Restoration Broomfield, CO
Rev. New 6-15-00
This tech paper will discuss the procedure for correct adjustment of the Minimum Idle Speed and for adjustment of the Throttle Position Switch (TPS) on the early C4 Corvette TPI systems.

These steps apply specifically to the 1985 model year, and in general to other years. Later model years do not have adjustable TPS's. General Idle speed and off-idle throttle response on the early TPI systems is determined by correct adjustment of the minimum idle speed screw combined with a correct setting of the TPS.

I've seen many of these cars that have had their idle speed corrected by well-intentioned mechanics and owners by simply screwing the minimum idle speed screw in a few turns. This really messes up the settings, and will not make your car perform properly. Doing a correct setup of the TPS is one of the easiest ways to make your car feel and respond better. To maximize the benefit of this procedure, I recommend that you first remove your Throttle Body (TB), disassemble it (it's incredibly easy, there are a total of about 5 pieces in it), clean the TB up really good with some spray carb cleaner, and put it back together.

A nice clean TB will really put an edge on the performance improvement you will get by doing this procedure. The Service Manual has instructions for doing these operations, but the directions are scattered through several sections of the Manual.

Here is the complete, step-by-step process for doing this (not including TB rebuild). All specs and steps are taken directly from the Manual (all 3 different sections), and this process is absolutely correct.

Tools & Equipment You will need the following tools and equipment:
1. A set of Torx wrenches. You can buy a complete set in a nice, genuine plastic pouch at Sears.
2. A good digital voltmeter that will read voltages less than 1 volt.
3. A paper clip.
4. A small screwdriver.


Procedure
There are two electrical components on the TB that you will be working with: The TPS and the Idle Air Control Valve (IAC).

Make sure that the connectors for these two components are easily accessible and that you can easily disconnect the IAC.

You will also be playing with the diagnostic connector under the dash. Remove the cover (if it's still in place). Bend your paper clip into a U shape. You will be playing with the two top right hand terminals (A and B) in the connector.
  1. First step is to set the minimum idle speed. If nobody has messed with this on your car before, the set screw will be covered by a pressed-in plug. It's located on the driver's side of the TB. Remove this plug if it's there.
  2. With the IAC connected and the ignition OFF, stick the paper clip into the diagnostic connector from A to B. This grounds the diagnostic lead.
  3. Turn the ignition to the ON position without starting the engine. Wait 30 seconds.
  4. Now, with the ignition still in the ON position, disconnect the IAC connector at the IAC.
  5. Remove the paper clip from the diagnostic connector.
  6. Start the engine and allow it to reach normal operating temperature. The idle speed will probably be really low, and you may have to coax the engine a bit with the gas pedal to keep it running for a while.
  7. If your car is an automatic, set the parking brake and put the transmission in DRIVE. If your car is a manual, leave it in neutral. · Adjust the idle speed screw to obtain 400 rpm in drive or 450 in neutral.
  8. Shut off the engine and re-connect the IAC. That's it for idle speed.

Now on to the TPS.

There are 3 wires stacked vertically on the TPS. You will need to be able to measure the voltage between the two top wires. You can either buy a special harness connector that breaks these wires out (from Mid America), or gently pierce the insulation of the wires with the pointy prongs on your volt meter. You can also stick a paper clip into each of the two top locations of the connector and clamp onto the paper clips to measure the voltage. Whatever is easiest for you.

  1. Turn the ignition to the ON position without starting the engine.
  2. Loosen the TPS Torx adjustment screws. · Set your volt meter to a low scale DC volt setting that will accurately read less than 1 volt.
  3. Measure the voltage between the two top TPS wires.
  4. Adjust the TPS by rotating its position until you get a reading of .54 volts.
  5. Tighten the Torx screws and recheck the voltage. Re-adjust if necessary to make sure voltage is right at .54.
  6. Turn the ignition OFF. You are now in perfect adjustment on idle speed and TPS output.

Start the engine. It may take a few seconds for the car to catch on to its new settings.

ID adjust the TPS and IAC and idle screw and get it to run at 650 rpm, then throw in a can of both texico fuel injection cleaner and sea foam gas treatment, yes they do tend to clean up varnish and crud in the injectors, but in most cases its WATER in the fuel thats a more common problem than crud, if your changing fuel filters about every two years or more frequently

http://www.thirdgen.org/tpimod2

http://forum.grumpysperformance.com/viewtopic.php?f=36&t=3453&p=26193&hilit=vats#p26193

http://forum.grumpysperformance.com/viewtopic.php?f=36&t=520&p=645&hilit=vats+resistor#p645

http://forum.grumpysperformance.com/viewtopic.php?f=36&t=63&p=31920&hilit=starter+rebuild#p31920

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=5926&p=18562&hilit=starter+rebuild#p18562

http://forum.grumpysperformance.com/viewtopic.php?f=32&t=1401

reading thru these links, and sub links should give you a great deal of related info, if your having problems starting or getting your engine to run

break down the problem in sections,
will the engine spin over?
does the starter work?
is there fuel in the tank?
is the fuel pump working?
are you getting oil pressure?
are you getting fuel pressure?
do you have 13 volts at the battery?
do you have voltage at the coil?
spark at the plugs?
are all the electrical connections good?
are all the fuses good?
get a code reader and a multi meter , pull codes check fuses and get a shop manual for your year corvette the auto parts store books leave out a great deal of info
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

User avatar
Site Admin
Site Admin
 
Posts: 14105
Joined: September 14th, 2008, 1:40 pm
Location: florida

Re: adjusting your TPS AND IAC

Postby grumpyvette » December 5th, 2009, 4:19 am

cleaning your IAC, WARNING
connecting your IAC to the cars wiring harness while its not properly installed in the throttle body, or trying to remove it with the wiring connected, will almost always result in almost certain over extension of the pintle and the components self destruction, it should be removed, cleaned carefully with throttle body cleaner spray(similar to carburetor cleaner spray), follow instructions below), after its cleaned and the throttle body is clean, re-install it into the throttle body BEFORE you connect it to the wiring harness

BTW its located on the lower side of the throttle body


http://www.ecklers.com/product.asp?pf_i ... pt_id=1279

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IDLE AIR CONTROL VALVE, located on lower pass side of THROTTLE BODY
http://www.lbfun.com/warehouse/tech_inf ... 0Paper.pdf

How to Adjust your Early C4 TPS and Idle Speed
by Lars Grimsrud

This tech paper will discuss the procedure for correct adjustment of the Minimum Idle Speed and for adjustment of the Throttle
Position Switch (TPS) on the early C4 Corvette TPI systems. These steps apply specifically to the 1985 model year, and in
general to other years. Later model years do not have adjustable TPS’s.
NOTE:
The Minimum Idle Speed sequence outlined in this paper is taken directly from the 1985 and 1986 GM Corvette Service
Manuals with some clarifications and simplifications added by me. Be aware that there are aftermarket manuals that outline a
different sequence. I have used the sequence in this paper and verified that it is correct for the model years noted. You may
choose to use the procedural sequence outlined and recommended by others.
General
Idle speed and off-idle throttle response on the early TPI systems is determined by correct adjustment of the minimum idle speed
screw combined with a correct setting of the TPS. I’ve seen many of these cars that have had their idle speed “corrected” by
well-intentioned mechanics and owners by simply screwing the minimum idle speed screw in a few turns. This really messes up
the settings, and will not make your car perform properly. Doing a correct setup of the TPS is one of the easiest ways to make
your car feel and respond better. To maximize the benefit of this procedure, I recommend that you first remove your Throttle
Body (TB), disassemble it (it’s incredible easy – there are a total of about 5 pieces in it…), clean the TB up really good with
some spray carb cleaner, and put it back together. A nice clean TB will really put an edge on the performance improvement you
will get by doing this procedure.
NOTE: If you disassemble and clean your Throttle Body, including removal and cleaning of the IAC, it is recommended that
you measure the extended length (protrusion) of the IAC “tip” before you re-install the IAC. If the “tip,” or “needle” of the IAC
(referred to correctly as the “Pintle”), is extending out too far, you will jam it into the seat and damage it during re-installation.
So before you install the IAC, measure the distance from the very tip of the Pintle to the surface of the IAC body that the gasket
seats against (with the gasket removed). The distance should be 28mm (1-1/8”) or less. If the distance is greater than this, you
must retract the Pintle into the IAC Body. There are two different styles of IACs:
If your IAC has a “collar” around the electrical connector end, simply push on the Pintle with firm hand pressure while rocking it
slightly side-to-side until it retracts.
If your IAC does not have a “collar,” compress the Pintle Retaining Spring towards the body of the IAC and try turning the
Pintle clockwise as seen from the Pintle end of the IAC. If it turns, keep turning until it retracts to the 28mm position. Then,
return the spring to its original position, with the straight part of the spring end lined up with the flat surface under the Pintle
head. If, however, the Pintle does not turn, use firm hand pressure as described above to retract it.
Once set up, install the IAC with the gasket and torque to 13 ft-lbs.
The Service Manual has instructions for doing the following operations, but the directions are scattered through several sections
of the Manual. Here is the complete, step-by-step process for doing this (not including TB rebuild). All specs and steps are taken
directly from the Manual (all 3 different sections), and this process is absolutely correct.
Tools & Equipment
You will need the following tools and equipment:
1. A set of Torx wrenches. You can buy a complete set in a nice, genuine plastic pouch at Sears.
2. A good digital voltmeter that will read voltages less than 1 volt.
3. A paper clip.
4. A small screwdriver.
Procedure
There are two electrical components on the TB that you will be working with: The TPS and the Idle Air Control Valve (IAC).
Make sure that the connectors for these two components are easily accessible and that you can easily disconnect the IAC.
You will also be playing with the diagnostic connector under the dash. Remove the cover (if it’s still in place). Bend your paper
clip into a “U” shape. You will be playing with the two top right hand terminals (“A” and “B”) in the connector.
• First step is to set the minimum idle speed. If nobody has messed with this on your car before, the set screw will be covered
by a pressed-in plug. It’s located on the driver’s side of the TB. Remove this plug if it’s there.
• With the IAC connected and the ignition “OFF,” stick the paper clip into the diagnostic connector from “A” to “B.” This
grounds the diagnostic lead.
• Turn the ignition to the “ON” position without starting the engine. Wait 30 seconds.
• Now, with the ignition still in the “ON” position, disconnect the IAC connector at the IAC.
• Remove the paper clip from the diagnostic connector.
• Start the engine and allow it to reach normal operating temperature. The idle speed will probably be really low, and you
may have to coax the engine a bit with the gas pedal to keep it running for a while.
• If your car is an automatic, set the parking brake and put the transmission in “DRIVE.” If your car is a manual, leave it in
neutral.
• Adjust the idle speed screw to obtain 400 rpm in drive or 450 in neutral.
• Shut off the engine and re-connect the IAC.
NOTE: Some later year GM Shop Manuals recommend disconnecting the distributor ECM wire (“Timing Connector”) near the
brake booster. This will prevent the ECM from altering timing – and idle rpm – during the rpm adjustment. Early GM Manuals
do not contain this step. If you disconnect the timing connector, you will get a Code 42 stored in the memory of the ECM. The
memory must be cleared of this code after re-connecting the timing connector.
That’s it for idle speed. Now on to the TPS.
There are 3 wires stacked vertically on the TPS. You will need to be able to measure the voltage between the two top wires.
You can either buy a special harness connector that breaks these wires out (from Mid America), or gently pierce the insulation of
the wires with the pointy prongs on your volt meter. You can also stick a paper clip into each of the two top locations of the
connector and clamp onto the paper clips to measure the voltage. Whatever is easiest for you.
• Turn the ignition to the “ON” position without starting the engine.
• Loosen the TPS Torx adjustment screws.
• Set your volt meter to a low scale DC volt setting that will accurately read less than 1 volt.
• Measure the voltage between the two top TPS wires.
• Adjust the TPS by rotating its position until you get a reading of .54 volts.
• Tighten the Torx screws and recheck the voltage. Re-adjust if necessary to make sure voltage is right at .54.
• Turn the ignition “OFF.”
You are now in perfect adjustment on idle speed and TPS output. Start the engine. It may take a few seconds for the car to
“catch on” to its new settings.
Questions, Comments & Technical Assistance
If you have questions or comments regarding this article, or if you notice any errors that need to be corrected (which is quite
possible since I’m writing this from memory…), please feel free to drop me an e-mail. Also, if you need any technical assistance
or advice regarding this process, or other maintenance issues, feel free to contact me: V8FastCars@msn.com
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: adjusting your TPS AND IAC

Postby grumpyvette » March 6th, 2010, 3:49 pm

you can plug the rear fuel rail connection,remove the 9th cold start injector and plug the port it mounts to on the intake, it will result in it taking longer for the engine to start and on occasion a trouble code but no harm to the engine, BUT the smart route is to upgrade the CPU this eliminates the need for the 9th injector, speeds up the computer and makes the engine run better

read this


the original chip,transmitted at only 160 BAUD, :crazy:

http://www.eecis.udel.edu/~davis/z28/ecm_swap/870chart.pdf


the ECM that came in 1986-1989 TPI Fbody's and Vettes is a series 1227165 (165). The ALDL data rate in this model can supply diagnostic data at 8192 BAUD.:thumbsup:

http://www.eecis.udel.edu/~davis/z28/ecm_swap/165chart.pdf

http://www.eecis.udel.edu/~davis/z28/ecm_swap/

http://home.earthlink.net/~gellett/7165swap.htm

http://www.eecis.udel.edu/~davis/z28/ecm_swap/relay_harness.jpg

http://www.eecis.udel.edu/~davis/z28/ECMs/85Fbody-wiring.pdf

http://www.eecis.udel.edu/~davis/z28/ECMs/85-870v8MAF.jpg

http://www.eecis.udel.edu/~davis/z28/ECMs/85_MAF_Burnoff.gif

http://www.eecis.udel.edu/~davis/z28/ecm_swap/ecms-photos1/ecm165memcalmod.jpg

http://www.eecis.udel.edu/~davis/z28/ecm_swap/ecms-photos1/enginebayrelaymounts85.jpg

viewtopic.php?f=32&t=168&p=202&hilit=+computer+1985#p202

viewtopic.php?f=36&t=63&p=76&hilit=+computer+1985#p76
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: adjusting your TPS AND IAC

Postby grumpyvette » September 3rd, 2012, 10:57 am

VADER POSTED THIS INFO"


There may be multiple problems, but the low idle RPM will affect the alternator output voltage as well as some of the other issues, so that would be among the first things to reconcile.

Throttle Minimum Air Position

Tools needed:
1. Torx driver # T-20
2. Paper Clip
3. Small Punch
4. Tachometer

GENERAL NOTE: The engine should be at normal operating temperature before performing any adjustments. Never rely on the dash mounted instruments for diagnostics and adjustments. The oil pressure and temperature gauges and the voltmeter and tachometer just aren't calibrated accurately enough for diagnosis, but are a relative indication for monitoring the vehicle while driving.

For this adjustment, the transmission will be in DRIVE while you're under the hood. You will need to securely set the parking brake and block the drive wheels. It would also be a good idea to have an assistant hold the service brake while you perform the adjustments.

In order to successfully complete the adjustment, the IAC air passages and pintle need to be clean. The throttle plates and bores need to be clean as well. If this is not the case, you'll need to remove the air cleaner from TBI engines or the intake air bellows from TPI engines to gain access to the area to be cleaned. A spray-type carburetor cleaner works well for this. Cleaning the IAC passages on a TPI/MAF engine will set a DTC, but we'll be clearing that later. With the engine idling, direct the spray cleaner in to the IAC air passages and around the throttle plates. Shut off the engine and continue cleaning the throttle plates by opening the throttle manually. Once everything is satisfactorily cleaned, replace the air bellows on TPI engines. Many times, this alone can solve IAC/idle speed problems.

If this doesn't solve the problem, you may need to remove and clean the IAC stepper motor. If the IAC appears to be clean and functioning properly, continue with the adjustment procedure.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Idle Air Control Cleaning

You can remove the IAC and service it. Remove the electrical connector from the IAC. Unscrew the IAC unit from the throttle body.

Very little apparent varnish and dirt accumulation on the IAC pintle rack gear can cause poor or no operation. This is a comparison between a completely "dead" IAC and a completely funtional one, after cleaning:



You can gently rock the pintle back and forth and allow the spring to extend it until it comes apart in your hands. Clean everything with lint-free cloths and a mild solvent. Harsh solvents can affect the insulation of the stepper motor coils. It's generally the dirt and buildup on this worm shaft that causes sluggish IAC operation.



Check the spring free length. Stretch the spring as necessary to get a minimum 2¼" free length. When the worm gear on the pintle shaft is clean and dry, apply one drop of clean light oil to the shaft, align the keyways with the keys molded into the IAC body, and work the pintle back into the rack gears of the motor by the same rocking motion. It takes a while to get the pintle back into the worm gears, but you'll get it. It is important to get the pintle fully retracted into the housing so that the pintle is not forced against the gears when reinstalling the IAC unit in the throttle body.

While the IAC is out, clean the air passages in the throttle body. The orifice in the TB where the IAC resides is the seat that the IAC valve closes against, and it can accumulate a lot of carbon, dirt, and debris. The easy way to do this is with carburetor cleaner and a small stiff brush.

When everything is clean and dry, replace the gasket if it is damaged, apply a little anti-seize to the threads, and torque the IAC to the proper specs. (13 ft/lb for '85-'89 , 30 in/lb for 1990-on.) Proceed with setting the TPS and minimum air position.

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

Locate the ALDL connector under the dash panel, in the driver's foot well area. Remove the plastic trim cover (if it is still there).



Cut and form a paper clip into a "U" shape. Insert the clip ends into the ALDL in the 'A' and 'B' sockets.



Turn on the ignition, but don't start the engine. This will force the ECM into its diagnostic mode. Wait 30 seconds to allow the IAC pintle to fully extend. Under the hood, remove the electrical connector from the IAC, then turn off the ignition and remove the paper clip jumper from the ALDL. With the IAC pintle fully extended (closed) all idle air will be controlled by the position of the throttle plates. Some manuals indicate that the EST bypass connector should be disconnected for this procedure, while some make no mention of it. While timing is a factor in idle speed, the EST should only operate as a function of engine RPM, temperature, and detonation sensor inputs. To remove all doubt, disconnect the EST bypass connector if your car is so equipped. Some TBI and V-6 engines do not have this bypass connector, and therefore must be set with no regard to the EST system. The EST can be bypassed on some cars by grounding the diagnostic terminal at the ALDL and continuing with the procedure, but the fuel mixture will be skewed to the rich side, affecting idle speed as well. In any event, the minimum air position idle speed range is wide enough to allow for some variations. As always, it is best to consult your service manual for the exact procedure for your system.

Locate the Torx screw on the left side of the throttle body. It may be equipped with a protective metal cap from the factory. This was intended to discourage adjustment. If the cap is present, use a small punch to knock it out. Once the screw is accessible, start the engine and place the transmission in DRIVE. Adjust the throttle stop to obtain 400 RPM with the transmission in "DRIVE" on an automatic transmission car, 450 in neutral on a manual transmission car, rotating the Torx screw clockwise to raise speed and counter-clockwise to lower speed. Once the idle RPM is set, place the transmission in PARK and turn off the engine.

Re-connect the electrical connector onto the IAC. Start engine. Idle speed should be governed by the ECM at approximately 600-650 rpm in "DRIVE" (for unmodified cars). Idle speed in NEUTRAL or PARK is less significant, and will be higher.



Throttle Position Sensor (TPS)

Tools needed:
1. Digital Volt-Ohm-Meter (VOM)
2. Breakout jumper wires or probes (make your own)
3. OPTION: AutoXray, Diacom, or similar scanner (will replace the VOM and jumper wires).

Turn on ignition, but don't start the engine.

With a diagnostic scanner: plug in the scanner and read the TPS voltage. It should be 0.54Volts +/- 0.07 VDC.

Connect the VOM to the TPS electrical connector terminals ‘A' and ‘B'.

With a breakout jumper: Disconnect the electrical connector from the TPS. Install the breakout in-line, between the TPS and wiring harness connector. Connect the meter probes to terminals 'A' and 'B' on the connector. (‘B' is the positive connection, ‘A' the signal ground, or negative.)

With probes: If you have very slender probes on your VOM, you can back-probe the TPS connector while it is attached to the TPS. If you have made probes of large dressmakers pins or a similar item, you can back-probe the connector as well. Connect the meter probes to terminals 'A' and 'B' on the connector.

Turn on the ignition to read the TPS output voltage at the idle position. The reading should be 0.54VDC +/- 0.07VDC. The ideal is the center of the range, 0.54VDC for a stock engine. To adjust the output voltage, loosen the two Torx screws holding the TPS to the throttle body, and slightly rotate the TPS up or down, reading the voltage until it comes into specification. Tighten screws. Using the throttle lever, rotate the throttle to WOT (wide open throttle). The TPS voltage should be over 4.0 volts. Close the throttle again, and then slowly open it to WOT, observing the voltage reading. It should increase progressively and in a linear fashion. If it sticks or jumps or falls off at all while doing this check, the TPS sensor may be failing and could be a cause of stumbling and driveability problems.

After achieving the desired setting, turn off the ignition switch. Remove all jumpers or the scanner and reconnect the TPS connector as required.

Reinitializing the ECM

If you set a DTC during the procedure, the SES light should be illuminated on the dash. This ECM retains DTC data for the previous 50 engine starts, so the codes will eventually be cleared. If you want more immediate results, after shutting down the engine disconnect the negative battery terminal for five minutes. This will clear the ECM of all diagnostic trouble codes. Clearing the ECM also clears any data learned about your engine, and clears the radio presets. If you have a Delco-Loc or Theft Loc II radio, make sure you follow the procedure to unlock the radio protection before disconnecting the battery. This five minutes is also just about long enough to clean both battery cables. Reconnect the battery. When you first start the engine after clearing the ECM, the engine will operate with base parameters programmed into the ECM PROM. These parameters may not be optimum for your engine, but the ECM will enter a Block Learn Mode soon after the engine is warm and enters Closed Loop Mode. The ECM will write new data tables specific to your engine and will eventually rely on those tables instead of the base tables of the factory program. You can expedite this process by driving the car for 20 minutes under varying conditions to allow the ECM to initialize. Or you can wait and drive the car normally at your convenience. The BLM tables are constantly being updated as sensor input ranges change, but the greatest change will occur within the first twenty minutes of Closed Loop operation."
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: adjusting your TPS AND IAC

Postby grumpyvette » August 8th, 2013, 2:04 pm

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: adjusting your TPS AND IAC

Postby bytor » April 6th, 2014, 8:49 pm

Hey Grumpy, is it normal for the IAC on my 87 vette to make a clicking/buzz sound when turning the key on? I’m pretty sure the noise is coming from the IAC because when I disconnect it, the sound stops.
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Re: adjusting your TPS AND IAC

Postby grumpyvette » April 6th, 2014, 9:05 pm

bytor wrote:Hey Grumpy, is it normal for the IAC on my 87 vette to make a clicking/buzz sound when turning the key on? I’m pretty sure the noise is coming from the IAC because when I disconnect it, the sound stops.


no! it sounds like its needs cleaning and its either broken or carboned up, but be aware that if you connect the IAC too the electrical harness wire while it is not installed in the throttle body housing and seated correctly and extended correctly it will self destruct as it over extends, or is manually compressed so read the directions on how its cleaned and re-installed

Idle Air Control Cleaning
You can remove the IAC and service it. Remove the electrical connector from the IAC. Unscrew the IAC unit from the throttle body.
You can gently rock the pintle back and forth and allow the spring to extend it until it comes apart in your hands. Clean everything with lint-free cloths and a mild solvent. Harsh solvents can affect the insulation of the stepper motor coils. It's generally the dirt and buildup on this worm shaft that causes sluggish IAC operation.
When the worm gear on the pintle shaft is clean and dry, apply one drop of clean light oil to the shaft and work the pintle back into the rack gears of the motor by the same rocking motion. It takes a while to get the pintle back into the worm gears, but you'll get it. It is important to get the pintle fully retracted into the housing so that the pintle is not forced against the gears when reinstalling the IAC unit in the throttle body.
While the IAC is out, clean the air passages in the throttle body. The oriface in the TB where the IAC resides is the seat that the IAC valve closes against, and it can accumulate a lot of carbon, dirt, and debris. The easy way to do this is with carburetor cleaner and a small stiff brush.
When everything is clean and dry, replace the gasket if it is damaged, apply a little anti-seize to the threads, and torque the IAC to the proper specs. (13 ft/lb for '85-'89 , 30 in/lb for 1990-on.) Proceed with setting the TPS and minimum air position.
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: adjusting your TPS AND IAC

Postby bytor » April 7th, 2014, 1:12 pm

Thanks Grumpy for the feedback. I was intending to pull the throttle body and give it a good cleaning anyway; I’ll check things out then.
I found another minor issue with the fuel pump relay connector. I’m currently not experiencing any problems with the fuel pump relay but I noticed the wires going into relay connector are exposed a little bit. It looks like the insulation has shrunk and exposing about an 1/8 inch on a few of the wires. Here’s a picture below that shows what I’m talking about. I found this on the internet that shows the exposed wires. Mine is not this bad.

Relayfaults.jpg


What are my options for repairing this?

Splice in a new connector pigtail like this.

images.jpg


Or do they make repair kits for the connector that includes replacement terminals similar to this one?

51N9vAfEY-L._SY300_.jpg


Any thoughts or other options?
You do not have the required permissions to view the files attached to this post.
My 383 build photos
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Re: adjusting your TPS AND IAC

Postby grumpyvette » April 7th, 2014, 1:27 pm

on almost all older cars electrical connector pigtails and connectors for repairs are available, your local NAPA may have them listed and be able to provide many (AT EXORBITANT PRICING BUT OVER NIGHT DELIVERY) which on a connector that should cost $1-to-$2 each but from them, it may cost $7-to -$20 each yet may still be worth the cost at times, to get the car back in service

viewtopic.php?f=36&t=3105&p=8272&hilit=connectors+pigtails#p8272

if you shop around carefully its quite common to find you can purchase a dozen or a bag of 50 connectors for the price NAPA or advance auto charges for just a few connectors
http://www.acdelcotechconnect.com/pi/wiring-connectors/gm/pigtails/

http://www.ecklers.com/search.asp?actio ... chHistory=

http://www.eficonnection.com/eficonnection/tpi_pigtails.aspx

http://www.repairconnector.com/products ... 4-AWG.html

http://www.acdelcotechconnect.com/pi/wi ... /pigtails/

http://www.suresealconnections.com/

http://www.garrettelec.com/kits/details ... NNWP25S617

viewtopic.php?f=70&t=1443&p=28051&hilit=shrink#p28051

http://www.repairconnector.com/

http://www.waytekwire.com/automotive-connectors.htm

http://www.rowand.net/Shop/Tech/Automot ... ectors.htm

http://www.vette2vette.com/
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: adjusting your TPS AND IAC

Postby bytor » April 7th, 2014, 3:21 pm

These would work right? Looks like there is a Pac-Con and a Pac-Con HD connector. Not sure which one but at $3.00 a bag, I can get both and redo the connector.

http://www.repairconnector.com/products/GM-Pak%252dCon-OEM-Repair-Terminal-Female-16%252d14-AWG.html
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