Hey all,

No idea why my IAC will not close and lets the engine run at an RPM above the setting. I have my idle set for 1000 rpm and sometimes, the IAC stays open and allows the car to idle at 1300 or something similar. The IAC will read 112 counts when it should be somewhere around 40 to get to 1000 rpm.

As I remember, there is no feedback from the IAC to the computer to confirm so this seems computer driven.

I have had it stay like this for weeks and then all of a sudden, it will act normally.

Thanks,
Ben

 

Is it possible your closed throttle TPS voltage is too high? That will screw up the PCM's control of the idle speed if its above 1.0V. Ditto with the VSS, if its not reading "0" when the car is not moving.

 

X2. I just had this problem with my car. IAC counts were around 130 and it was idling 1000rpms too high. I checked the tps and it was reading too low at .02v and 20% throttle at idle. The computer only closes the iac when the throttle is at 0% because it has no reason to close while you are moving. In my case, the tps was actually bad. You may want to check into it

 

It actually elevates the idle speed when the vehicle is moving, to prevent the engine from stalling when the throttle closes suddenly. And when it senses you have intentionally opened the throttle, it lets you take control.

 

Speed reads 0 when I am not moving.

Voltage is 0.75V with a closed throttle. Should I do the TPS mod and get that down a little bit? Ah, looking at my data, I may have found a relationship. I have the throttle cable so tight that when the car warms up...sometimes, the throttle will indicate an open position of 0.8%. I will adjust and report back.