As soon as i think all the bugs are worked out, more seem to pop up My car has a high idling problem after it warms up. I've closed the throttle blades and slotted the tps sensor so its still in spec, but it hasnt fixed the problem. When the car is cold, it will idle right around 900-1krpm (tuned for 900). But as soon as the car begins to warm up, rpms rise to about 1800. :wtf: I checked the iac counts and it was 150 when cold, and still 150 when it warms up and gets to 1800 rpms. I reset the iac using shoebox's method and now it reads 60/61 (1k rpm and 1800 rpm). When the rpms are 1800, shouldn't the iac counts drop to 0? Even if the iac wasnt working, shouldnt the pcm counts still read 0 since it SHOULD be trying to get it to close?

I didnt have this problem before I changed my opti/coil/icm/wires (not that i think any of those things could affect it, but it did sit for about 1 month during the process).

I've checked and checked for vac leaks and have found nothing.

fyi checked the coolant temp sensor in the water pump and it is working correctly

Any suggestions?
thanks in advance

 

Update: Started the car and while it was idling around 1200rpms, I turned the steering wheel to put a load on the motor and it dropped about 200rpms while I was doing so. This leads me to believe the iac is bad. Why aren't the counts moving though? Shouldnt they still move even if the iac doesnt, since the counts are what the pcm is telling it to do?

 

A favorite place for a vac leak is the part of the tb gasket underneath. Other than that what is the IAC closed voltage? Should be .6 volts taken off the blue wire (if I remember correctly).

Hal

 

Ya I thought about the tb gasket since i've taken the tb off about a dozen times now. Ill change that and update. Im pretty sure its not a vac leak because the iac counts should be dropping to 0 if that were the case. Worth a shot though. Ill also look into the iac voltage. Thanks Hal!

 

Sorry, didn't mean the tb gasket. I meant a portion of the rubber elbow that goes underneath the tb. It gets caught inside the tb sometimes.

Hal

 

You're confusing the IAC motor with the TPS sensor. The IAC is not a sensor, its an actuator. All you can do is check the resistance of the windings (use method on Shoebox's site) to see if they are shorted or open.

The OP is correct. The PCM is not responding to the high idle, as it should (close down by commanding lower counts). That can be caused by lower than actual coolant temp sensor signal (appears to have ruled that out), a VSS signal that does not = "0" (PCM thinks the car is moving and elevates the idle RPM) or a TPS voltage that reads higher than 1.0 (which is maybe what you were trying to say??).

Is the tach reading correctly? Are you reading the engine RPM from the tach or the PCM?

 

The coolant temp shown in freescan is consistent with the gauge on the dash and they both appear to be normal. The tps voltage was really low (.06) so i slotted the sensor and raised it up to about .75. <no change. If the vss did not =0 it would be shown via the speedometer correct? If so, its fine.

Im looking at the rpms via the tach and pcm in freescan and they are both roughly the same

 

I just checked the tps again while the car was running. At idle the % is going anywhere from 0 to 25. I shut the car off and played with the tb while watching the tps; WOT is a consistent 4.7v and 100% but when i close the tb it drops to .7v and sometimes it drops as low as .04v. The tb isnt getting hung up so im thinking a bad tps sensor might be the answer to my problem.

If the tps was reading 20% at idle, the pcm wouldnt be closing the iac because it thinks im giving it 20% with the pedal, correct?

 

Yes. When the engine is above idle conditions, the PCM raises the IAC counts to prevent the engine from stalling when the throttle closes suddenly. The PCM doesn't see anything wrong with the engine running at 1,200rpm or 1,800rpm when the throttle is not closed, so its not going to close down the IAC valve.

You should be getting an SES light and a code for any TPS reading under 0.20V. I'd say you have a problem with the TPS sensor or the wire.

 

Problem solved! I changed the tps and everything is great now. Thanks alot for the help!

 

Was the sensor you replaced a GM unit? What did you replace it with?

 

no i got it from autozone, its a "duralast" brand. It was <$25 with a 2year warranty