Hi everyone, I am having a problem adjusting my idle speed. It idle's pretty good, at about 600rpms. When I try to remove the IAC connector to adjust the idle speed, the car just starts up and dies, almost as if it has a vaccuum leak. It just won't stay running. Then if I connect the IAC and remove the jumpers from the ALDL, the car will start and die a few times but then it will start and run fine. I've also noticed that my car cranks for a long time before starting. I tested the fuel injectors and they all read about 16-16.3 ohms. I don't think its my cold start injector because if I wait just a few minutes, sometimes the car starts, sometimes it cranks for a few secs and then finally starts. To my knowledge the car has S/R heads, hypertech chip, and maybe a cam. Its an 88 IROC. Sorry for the long post and thanks for any help ahead of time, Ihab

 

my iroc did the same thing when i reset the idle speed, i just started it quick and manually opened the throttle lever while i adjusted

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89 iroc 5.7 can't go fast enough. 14.1

http://www.picturetrail.com/irocsean

 

is the car at normall operating temperature while adjusting idle speed?

 

Yep usually the car has been running for a while before I try to adjust the Idle air.

 

I am having the same problem. but I just swapped TB and runners. Someone suggested that the IAC passage might be blocked by the gasket. Will pull off tonight and see. But the exact same symptoms (with a new IAC).

Jim Buckingham

 

First of all..... the idle screw shouldn't be touched... if the engine pulls to much air through the throttle plate (butteryflys) then the IAC will be running way out of spec.... it is best to leave that to a dealer, they have a diagnostic computer they hook up and can tell what the IAC is running at, and they can adjust the idle screw accordingly... It is imparitive to have the IAC running at proper range.

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 113,000kms

 

Check out this link

http://www.f-body.org/oldfaq/html/tech/index.html

Click on IAC resetting under section #2, (you have to scroll down to find it).

Basic procedure:

1. Warm up engine to operating temp(very important)
2. Shut off engine
3. Disconnect Timing advance wire (located by the blower motor)
4. ground ALDL terminals A&B (the fans should come on and SES light should be flashing when the key is turned on)
5. Turn on key, but do not start car, wait 30-40 seconds (the IAC is going fully closed at this time)
6. Disconnect the IAC connector
7. Pull the Jumper from ALDL
8. Start the Car (you may have to have someone start for you and idle the engine down slowly) set the idle to around 450 (I used a pair of pliers to "tweak" the tab that the throttle screw sets on versus pulling the plug and setting the screw itself) Using a different tach is not a bad idea either, the stock on in the dash is not real accurate at this range.
9. Shut off engine (key to off) and reconnect IAC connector and timing connector
10. Disconnect battery for at least 1 minute
11. Connect battery, turn key on for a few seconds and then turn off (dont start engine)
12. Turn key on and start engine
13. IAC should be set,however it may be needed to drive arounf for a few miles to allow the ECM to get accustomed to the IAC

HOWEVER: Before you do this I would suggest the following
1. Pull air intake ducting off of throttle body and hold throttle to wide open (engine off of course!)
2. Using a rag soaked in carb cleaner, clean the throttle bores and the edges of the throttle plates


TPI engines get a lot of carbon in this area, especially high milage motors.

This will ensure proper air flow.

Sorry so long, I hope that this helps.

Diesel

[This message has been edited by diesel (edited September 21, 2001).]

 

Yep, that's good advice on setting the IAC and minimum air setting. The trick is to start high and lower the rpms until you get the setting you want.

Also, you might want to check on this for your car, but I read a while back that GM issued a service bulletin raising the minimum idle speed - IAC disconnected - by 100 rpms for the L98. I don't know if that recommendation effects all years though.

Hope this helps.

Jake

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1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9, TPIS Long Tube Headers and DynoMax Super Turbos (HATE 'em)