Here is a chance to demonstrate your superior knowledge, "about these motors!". Explain to us WHY:. Feel free to get technical and to quote your FSM.

When you have carefully, and logically documented your reasons for making the adjustment, only, on a cold engine, 'splain how that makes it run quicker than "14's and 13's in the 1/4 mile".

RACE ON!!!

 

Because.

Because.

 

good one

 

I'm afraid that is exactly (or the equivelent) to what we'll get...if anything.

RACE ON!!!

 

Since I hate it when people get a problem fixed after asking for other peoples help and NOT posting what the fix was here it is:
Turns out (embarrassed) I didnt unplug the IAC when setting the minimum idle. I had a brain fart and unplugged the TPS instead(I know MUCH better). :o
Thanks Again!
Chris

 

I deal with crap all day I don't need it here stick it!
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 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.

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.

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.

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.


Bite me.



General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.

© Copyright General Motors Corporation. All Rights Reserved.

 

Glad it's fixed - just don't forget there's probably a 22 stored in History if you ran it with the TPS disconnected. Might want to clear it so that it doesn't pop up the next time you scan it and leave you wondering - "where in the hell did that come from?".

 

Is that short for saying, "I can spout any nonsense I want to without justifying it"?

I'm not sure how a "Restoration" article starts a procedure that ends with a disclaimer from GM, but that's OK. How does this post back up or justify:Your backup, justification, quote says, in case you need reminding:Are you saying that, "Start the engine and allow it to reach normal operating temperature and "You can only set the idle when the engine is cold" have the same meaning? Tell us zactly, what it is that you are "More positative than any one could ever be about anything !" about.

RACE ON!!!

 

I was kinda wondering that myself. I was all set to try it with the engine cold when I read this contradiction, for once I'm glad I put something off.

 

So let me see if I have this right. You give out incorrect advice, then when you are corrected you tell people to stick it?



You may want to take a few of these.

 

Come on guys, crap like this is why people dont post as much here anymore. We should all be civilized to one another, sometimes wrong advice is given out, out least they tried to help. It is fine to correct someone but dont be rude, thats not why we're here.

 

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.


Looks like the first step to do is when engine is cold

 

Who is getting uncivilized? Some very incorrect and possibly, harmful to the uniformed, information was posted and when asked if he was sure, backed it up with, "More positative than any one could ever be about anything !". Is that civilized? I merely asked for an explanation as one who, "You are just showing you nothing about these motors!" (whatever THAT means?). Us ignoramuses (this one, anyhow) like to be set straight, so I asked, "Here is a chance to demonstrate your superior knowledge, "about these motors!". Explain to us WHY:The only answer I saw was one HE posted contradicting what he is, "More positative than any one could ever be about anything !"

I think the RUDE was on the other foot.

RACE ON!!!

 

If the bickering is ignored this is actually a very informative post thet will be very helpful that will help anyone who needs to set their idle speed on an 89. Come on guys ...... everyone can make a mistake now and then ........... lets at least keep it civil.
Jerris

 

The IAC COULD be disconnected and then the minimum air adjustment made after the engine warmed up. But there is no reason the IAC can't be disconnected AFTER the car is warmed up. It will save having to nurse the cold engine through warm up without a fast idle working. To actually try to SET the minimum air adjustment on a cold engine is absolutely ludicrous.

RACE ON!!!

[EDITED]For clarity

 

I'm not sure with my L98, I have never felt the the need to reset the IAC. When I had problems with my LT1 Camaro resetting the IAC with the engine cold always seem to take better than resetting with the engine warm. "WHY" I could not tell you and really don't care it just worked.
I'm hoping to RACE ON soon!

 

You need to go back and do some rereading, more slowly, maybe. None of this discussion concerns resetting the IAC. You are right, the IAC does NOT require periodic resetting. It only needs to be "set" after it has been replaced or reinstalled. All of the above ASSUMES that the IAC is set and operating properly. THIS discussion is on setting the "minimum air adjustment". Big difference.

RACE ON!!!

 

Your goal isn't resetting the IAC, you are disabling it so that the IAC isn't controlling idle speed. Without the IAC enabled you can then set your minimum idle speed using the screw.

As CFI said you can disconnect it when cold then you have to nurse the car because it is getting no computer cold start help from the IAC.

As far as being civilized, when someone giving wrong advice tells the people to "stick it" that try to correct him I think the rude is on the other foot.
If you recall I was told I didn't know anything about "these" motors, and that was coming from the guy who knows "how to do it right."

 

According to the posted instructions you reset the IAC first before setting idle, removing the paper clip does not disable it.
You my not think so but you do come across a bit harsh or strong when posting and that is why some may bite back. Not me I could care less.

RACE ON!!

 

When you put the paperclip in you are setting the IAC to a fixed position, you aren't resetting it. When you unplug the IAC it no longer can be moved by the computer so that is when you remove the paperclip.
If you try to set idle with the IAC attached the pintle will just move to compensate and try to maintain the idle speed set on the chip.
If people are going to get upset with him asking them to defend their postitions they better be sure that they are correct.
Not that I would ever disagree with him.
160 stat <cough>