Anthony Boni
5+ Year Contributor
- 212
- 23
- May 13, 2018
-
Wrightstown,
New Jersey
So long story short, I’ve been chasing an ISC issue in my car for several months on and off. I remove the ISC from the car and turn on my power, the ISC just vibrates. This goes for all 3 of the ISC motors I’ve tried. With the car running, the ISC motor starts at 120, slowly descends to 0, then slowly ascends back to 120. It repeats this the entire time the car is running. I’ve also left one ISC motor installed, and plugged in another ISC and sat it on top of my valve cover. Link showed the ISC position changing, but nothing was happening to the ISC motor sitting on the valve cover. It was just vibrating ever so slightly. Unplugging the ISC with the car running makes no difference in the way it idles.
It’s a 1990 DSM with a 91+ TB. I’ve swapped the two wires required when running the newer throttle body and ISC. I’ve sent my ECU to ECMTuning and they fixed a few things and sent it back. I’ve replaced the ISC motor 3 times. I’ve checked for resistance in the wires from the ECU to the ISC plug. I’ve checked I was getting 12 volts to the two power wires at the ISC plug from the MPI relay. I’ve ohmed out every one of my ISC motors. All of this, and I’ve found nothing wrong.
The only thing I can think of that can possibly be wrong is my ECU! It’s not my ISC(s) and it’s not my wiring. I trust the guys down at ECMTuning, but I’m hoping they overlooked something because I am losing my freaking mind trying to figure this out.
Some other things I’ve done before I’m asked: Compression tested the engine, leak down tested, boost leak tested, smoked the intake manifold, all new timing components, Verified base timing. Everything else on this car is PERFECT. I just can’t figure out this ISC problem!
I’m running speed density with an Omni 4 bar straight off the intake manifold (no Ts) as well as a GM IAT sensor.
What else could there be? Please help me!
It’s a 1990 DSM with a 91+ TB. I’ve swapped the two wires required when running the newer throttle body and ISC. I’ve sent my ECU to ECMTuning and they fixed a few things and sent it back. I’ve replaced the ISC motor 3 times. I’ve checked for resistance in the wires from the ECU to the ISC plug. I’ve checked I was getting 12 volts to the two power wires at the ISC plug from the MPI relay. I’ve ohmed out every one of my ISC motors. All of this, and I’ve found nothing wrong.
The only thing I can think of that can possibly be wrong is my ECU! It’s not my ISC(s) and it’s not my wiring. I trust the guys down at ECMTuning, but I’m hoping they overlooked something because I am losing my freaking mind trying to figure this out.
Some other things I’ve done before I’m asked: Compression tested the engine, leak down tested, boost leak tested, smoked the intake manifold, all new timing components, Verified base timing. Everything else on this car is PERFECT. I just can’t figure out this ISC problem!
I’m running speed density with an Omni 4 bar straight off the intake manifold (no Ts) as well as a GM IAT sensor.
What else could there be? Please help me!
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