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90 C4 Won't Idle at Cold Temps

C4 Scan and Tune - forums.corvetteforum.com
Hey Guys (and Gals),

I bought a pristine '90 C4 a couple of weeks ago with 80K on it. I've been driving it daily without issue. Friday night, I parked the car as normal. Saturday morning, it wouldn't start. I checked the fuel pump, and it was working. I had compression as well. I did some digging, and decided to replace the ICM and the rotor. After that, the car started- but wouldn't idle! I feathered the accelerator for a bit, and when the car heated up to around 190 degrees, I could take my foot off the pedal and the car would maintain an even idle on its own. If I shut it off, I could start it with no problem, and it would idle on its own.

This morning I went back out to drive the car to work (it was cold out), and again, it wouldn't maintain an idle on its own. I warmed the car up, and drove it to a repair shop. They haven't been able to find out what's causing this? Do you guys have any thoughts? This is my first Vette, and I'm looking at it like a learning experience- or, as my one car buddy said it, "Daily driving a C4 is considered an extreme sport by most people."

ANY help would be appreciated. My thought is maybe it's the throttle position sensor...?

Thanks in advance.

I'm starting to wonder if it's not the Coolant Temp Sensor? I noticed my second fan does not turn on, even with the A/C on. Could that be sending faulty signals to the ECM and causing issues with ignition, idle, and that second fan? I bought the FSM but it hasn't arrived yet.

Is this the culprit? It leads back to what I think is either the MAF Burnoff Relay or the MAF Power Relay, and I bet it was connected to that terminal.


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