minimac

I have a 88' GT, 5 speed. here's the hoe-down,
a few months ago the car would sometimes raise it's idle to upwards of 3000k by itself at a stop light or something. The car started perfect in any condition, and idled perfect. the guys on here say replace or clean the IAC, i replaced it with one from autozone. Problem was still there, did change a thing so i guess my old iac was fine. I did not drive the car most of summer (no a/c) but now that school started back up, i had to fix that holding idle problem. i replaced the tps, and did the idle reset (warm up car, unplug iac, set idle with screw to about 650-700, plug back in, restart no acc., restart with acc.) the hanging idle problem went away! thank god, flipping the key off and on at every stop light was a pain!! however, now when i start it, it seems like the computer will not use the IAC valve at all, if it's a cold morning, it runs like a carburetor car. i have to rev it and keep it running for about 5 mins before it will idle without dying. After school when the car has been sitting in the sun and it's about 80 degrees out it will start and idle, but it still will not raise the idle at all, not even at first. i crank it over and it immediately tries to idle at 700. It seems the computer doesn't know that there is an IAC valve on there. Please help! this car is driving me insane, to the point where im considering selling for a newer model.

javila2468

sounds to me that it could be your coolant temp sensor (NOT THE SENDER).

minimac

Is this the one that is on the heater core pipe??? It's almost right under the throttle body?

javila2468

on passenger side of distributor on lower intake. right behind the thermostat housing.

minimac

I have found the sensor. I have tried removing the plug on it and cleaning the contacts and spreading them apart for a better connection. It just is very strange how the car ran fine until i did the idle reset thing. Now it seems that the IAC valve is not functioning at all. everything else seems fine, no surges or anything, it just refuses to use the iac valve.

javila2468

have u checked for any vacuum leaks?

minimac

I have checked every vacuum hose i could find. like i said the car was fine until i replaced the TPS and reset the idle.
Ever since then it will not use the IAC at all. In other words, the computer cannot/will not control the idle at all, in any way shape or form.

The car runs off the idle screw on the bottom of the throttle body and thats the only thing that controls the idle, no matter what the situation.

The IAC valve is less than 3 months old and it worked fine until i reset the idle because i put the new tps on.

mattdel

Run KOEO/KOER tests. The computer forces IAC involvement during KOER and will record a fault for it if it's not working.

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