I have an 89 Iroc with a rebuilt 350, now 355. Yesturday I just put a new alternator on the car and when I went to start it, it was running kind of rough. My father and I decided to readjust the tps sensor thinking that since the old alt. low voltage problem affected it somehow. After we adjusted that and went to start it, it idled at about a little over a 1000. So I proceded to reset the IAC. After doing that, the idle went back down to a little below 750 in park and a little below 600 in drive.

But here is my problem, turning the car off after getting it to idle correctly and than restarting it results in the car to idle up at over 1000 again. I have reset the IAC 3 times with the same result.

Going back to the TPS sensor, according to the tech article here it should be at .54 +-.075. Our lousy volt/ohm meter only gives me the .5 and it fluctuates from .4 to point 6. Which I assume would be correct seeing that .54 minus .075 would give me my .4 and .54 plus the .075 would give me .6. Although when I put it to WOT it doesn't go to 4.0 it only goes to 1.0. The chiltens book doesn't say anything about testing it at WOT, it just says adjust it to .54 at idle.

All the engine sensors have been replaced with a years time, majority coming this last winter/spring when we rebuilt the engine. Only sensor we havent replaced is the maf sensor.

Any help would be greatly appreciated!
Thanks a bunch,
Steve

 

SPearson,

There are a couple things you might need to change.

First, adjust the throttle minimum air position AFTER the engine is fully warmed. If you set it cold, or before the CTS gets to 176°F, you're wasting your time since the ECM will be adding RPM and spark advance beyond the hot target idle speed.

After the air position is correct, set the TPS with a DMM with better resolution, and preferably one that is calibrated.

Realize that the ECM will idle the engine higher than target settings for up to a minute after it is started, even when at full temperature. Unless you want to do a major re-write of the PROM, there is little you can do to change this.

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Later,
Vader
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"Let the bodies hit the floor!"
Adobe Acrobat Reader

 

Well that is one thing I did wrong, I set the minimum air while the engine was still cold. One more question though, When I am setting the minimum air position, do I keep the a and b terminals ground while getting the engine to idle at 450rpm, or do I take the paper clip out to do that. Curious because I remember reading that it could cause harm to the ecm to run the engine with the terminals ground like that.

[This message has been edited by spearson (edited July 03, 2001).]

 

Get some TPI intake cleaner spray, it's diff. from carb spray. Anyway, the channels on ur TB might be clogged, that's wut messed my 305TPI up for a while, not he IAC.

 

Take the paper clip out BEFORE YOU START THE ENGINE and leave it out while you are setting minimum air. Leaving the A & B terminals grounded while starting the car can seriously **** UP the ECM. You can again ground the ALDL after the car is started to put the ECM into field service mode but since the ECM runs the car differently while in field service mode you should not ground the A & B terminals while setting minimum air.
bsa

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"If they do not run, Then they will die." - Stonewall Jackson
#3
'87 IROC, 355 TPI, Converted to SD, 700R4, B&M Megashifter, 3.42, Trick Flow Twisted Wedge Heads, Edelbrock Intake, Accel Runners, Comp Cam, Crane Gold rockers, Lucas 24# injectors, Edelbrock headers, Flowmaster 3'' exhaust, Mallory Ignition, Transgo Performance Shift Kit, Corvette Servo, 2,000 Stall Torque Converter

[This message has been edited by irocbsa (edited July 03, 2001).]

[This message has been edited by irocbsa (edited July 03, 2001).]