Bobwhite85

I need to reset the idle on my 1985 L98, I saw Vader86's C4 Technical Page website (WOW!! THANKS FOR ALL THE GREAT INFO Vader86!!) On his website he has how to reset the idle on a 1989 L98. Is that the same procedure that I would use on my 1985 L98??

SORRY people, new vette owner here, I will be asking alot of questions

THANKS FOR ANY INFO

CFI-EFI

I haven't read his web site, but you don't set the idle speed for either year, with the stock or a mild cam. The idle speed is burned into the chip. Any effort to change the idle speed should be done by burning a new chip.

You can learn a lot about how different systems of your car operate and interact with one another, besides saving you a bundle in misdiagnoses by picking up a FSM Factory Service Manual.

RACE ON!!!

vader86

This is basically a TPS/IAC resetting, so that the ECM controls it properly. You may also look at the other one, on cleaning and resetting the TPS/IAC. There are 2 pages, one written by Sam Lam.

I dont see why it wouldnt work for 85.

Bobwhite85

Ok, Thank you!! I just got the car did a tune up and fixed about three vacuum leaks and my idle went up to 1200rpms so I turned it down via the little torx screw on the TB. After reading your site I see that was wrong. So I was just going to start from scratch and reset it. That is a very uesfull website you have there THANKS!!

CFI-EFI

It as MORE wrong that you COULD change the idle speed with that screw. That is a definite sign that someone that doesn't know what they were doing has been playing in there before you get the car. With the minimum air adjustment properly set, the IAC should pretty much maintain the prom idle speed. Do follow the minimum air, IAC and TPS adjustments procedures from vader, or better yet your own FSM.

RACE ON!!!

_twisted_

A sure way to tell is if the cap covering the min idle screw is gone

CFI-EFI

The cap missing is a sure sign of the screw having been accessed before, but the proof that it has been messed with by someone that doesn't know what they were doing, comes from being able to lower the idle speed from 1200 rpms, with the throttle stop screw.

RACE ON!!!

pcolt94

So then what would be the criteria for setting (or re-setting) up the throttle stop screw. Is there a TPS on that year car which you would set up a specific voltage for minimum throttle stop point?

_twisted_

I would say the criteria just for sh!tzand giggles would be to go through the procedure of parking the IAC and verifying the min idle, if it doesn't need an adjustment then move on and check the TPS voltage. If it does ned to be adjusted, you'll have to reset the TPS to the proper voltage for your app.

If you have a 94, I dont think your TPS is adjustable from the factory

Bobwhite85

Yes, It was gone

pcolt94

Thanks, I was just asking for general knowledge on that 85, not my 94.

RRT vette

Yes, the 85 is set with the same procedure as on Vader's web page. Anytime the idle screw on the TB is turned, it will also change the voltage reading at the TPS. Follow the procedure and the idle should come down as long as there is not other problems.

CFI-EFI

The ONLY criteria for setting (or re-setting) the throttle stop screw is to make the minimum air adjustment.



Once the minimum air adjustment is made, the adjustable TPS (1984 - 1989) is set to spec. In the 1990 and up, non-adjustable TPS cars, the computer will make the compensation, internally.

RACE ON!!!