Car doesnt want to Idle - Team Camaro Tech
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post #1 of 3 (permalink) Old Mar 29th, 08, 06:49 AM Thread Starter
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Car doesnt want to Idle

My car does not want to idle and I cant figure out why. Once you start it up you have to give it gas to keep it going. Once you let off of the gas the car will start to stumble and then slowly will die. The odd part is that every now and then this problem wont happen and it has idled good. I set the timing to about 5 degrees adv. I have installed a different cam into the motor 260/260 .444/.444 112LSA and the car is computer controlled. Can this be causing my problem? What should I look into? Car is a 1985 Iroc-Z 5.0 TPI.
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post #2 of 3 (permalink) Old Mar 29th, 08, 06:59 AM
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Location: Yorkville, Illinois USA
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Re: Car doesnt want to Idle

you're gonna need more timing, but on a computer controlled car, the physical timing setting is actually a "reference" for the trigger to the computer. I don't know what it's supposed to be for a TPI system, my holley system wants a 10 degree reference, and a lot of stuff in that system is based off TPI era GM electronics and procedures.

I am pretty sure there is a wire you have to disconnect at or near the distributor (disables computer controlled timing) to set the base reference timing.

You might do somne reading here: These guys sell RT Tuner, a popular tuning program for GM based EFI.

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post #3 of 3 (permalink) Old Mar 29th, 08, 10:43 AM
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Re: Car doesnt want to Idle

According to a dissasembly I have of a couple different TPI controller programs, the base spark reference is 6*. Of course the actual base idle setting will be higher, but that is what the ECM expects the reference to be set to (for the program I have at least).

It's best to consult a service manual to be sure. is where I got a majority of my TPI knowledge. I know there is a base idle speed setting procedure and info on diagnosing idle air control motor problems as well. I'd suggest searching thirdgen for the idle speed adjustment procedure which will help determine if the IAC motor is working correctly or not. You might also want to check your plugs to see if any are more black than others. It's common for the fuel regulator diaphram to rupture also. Pull the vacuum hose off the pressure regulator and see if it's wet with fuel.

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