Idle speed problem

[cevic]

I have followed the step VFAQ site has shown to adjust the idle speed of my galant vr-4. I have set the the idle speed to ~800rpm with the two pins grounded. But as soon as I de-ground these two pins and let the computer to control the idle, the speed is still ~1100rpm even after 10 minutes of running. I just replaced the ISC motor with a newer model (black plastic housing, maybe a 2G unit). The resistances on this ISC is ~39ohms across the pins as opposite to 29~33ohm of metal housing type ISC. Do you thinki the ISC I am using is not compatabled with IG system?

 

[steve]

Why did you change the ISC?
Do you have a datalogger? What are the ISC steps once the car warms up?

Steve

 

[cevic]

The stock one was blown. I do have a logger and I will check the stepping value tomorrow.

 

[steve]

Did you repair/replace the ECU drivers for the ISC or at least check them?
If the ISC fails with the windings shorted they take out the ECU drivers.

Putting a new ISC on in that case does nothing.

Steve

 

[cevic]

I was thinking the same thing and bought some new driver IC. But all the IC (IC04-IC09) on the broad did not show any sign of burn or damage so I did not replace them. BTY, is it normal to have ~39 ohm across all the pins in a plastic style ISC?

 

[steve]

Is it normal to have ~39 ohm across all the pins in a plastic style ISC?

Yes.

Just because the part doesn't look blown doesn't mean that it isn't. I've replaced a bunch that looked good but couldn't pull the line low when you tested them.

Steve

 

[cevic]

Problem fixed. I spent like one and a half hour to replace the driver chips. Put it back in the car and nothing had change. So obviously the problem wasn't the ECU. I then checked on the engine bay and found that the tension of the throttle cable was too tight that the throttle couldn't retract all the way back. I then adjusted the nuts to loose the cable a little bit and problem solved.