Idle question for 1989 L98

[hpbadger]

I have been monkeying with my throttle body and am trying to find out what is the correct idle speed for a stock L98. I can't seem to find in in the service manual. When my car starts it settles in at about 500-600 rpms in park. Today I drove across town through traffic and it seemed stuck on 1000 rpms in drive after a while which seemed a little high. Thanks!

 

[EttevroC]

That sounds about right, my 89 L98 hangs around 500 at idle when it is warming up, and about 800 when it is in gear and running on level roads.

 

[vigman]

5-600 is correct

If it's running around 900-1000 you MIGHT have a vacuume leak OR your bushing around the butterfly are GONE....
OR

The IAC is just GOOED with carbon... try an IAC cleanout & relearn.

Food for thought....

Vig~

 

[vetteboy86]

Yeah I agree. Mine in fast idle will start at around 1000, and gradually settle in at 600. I feel this is right for the car. As for the actual rpm setting, I dont know. It shouldn't be that high when warm.

Craig

 

[Hib Halverson]

The curb idle speed is controlled by the engine computer using the IAC.

That said, there is a mechanical idle adjustment which I think, back then, was called "minimum air." Typically, minimum air is only adjusted if the throttle body is changed or the existing minimum air ajustment was changed for some reason. The factory Service Manual should have the specification for minimum air.

DO NOT attempt to control curb idle with a throttle body adjustment.

If minimum air is set correctly, the IAC is working properly and the TPS is in good order bit the engine will still not idle properly, start looking for a problem with the throttle body (such as worn shaft bushings or coke deposits,) a vacuum leak or other possible causes listed in the service manual.

 

[582Boat]

Idle Problem

Time After Time The Question Concerning Idle Problems Come Up, I Would Attempt To Run Some Carb And Throtle Body Cleaner Through Before Adjusting Anything.

 

[redc4corvette]

http://www.corvetteforums.net/tech/throttlebody.html

 

[hpbadger]

If it's running around 900-1000 you MIGHT have a vacuume leak OR your bushing around the butterfly are GONE....
OR

The IAC is just GOOED with carbon... try an IAC cleanout & relearn.

Food for thought....

Vig~

It is not doing it anymore. I reset the new IAC and calibrated the new TPS.
Maybe the computer had to relearn how I drive...my guess. Thanks again!

 

[tyrel]

It is not doing it anymore. I reset the new IAC and calibrated the new TPS.
Maybe the computer had to relearn how I drive...my guess. Thanks again!

This will happen if you disconnect the battery, the ECM has to start over from scratch. Whenever I unplug my battery to do any electrical work, and then start the car later, the idle is all over the map. After driving for a few minutes, everything resets itself.