weird idle problem

[Rieman]

Until the car is fully up to normal temp the idle will stick at 1500rpm and sometimes more and does this while driving so it's like the gas is stuck but it ain't. If I unplug the IAC this doesn't happen but I just bought a new IAC and still have this problem. Even the rpm's don't drop when I push the clutch in they at times go up. I heard that maybe the problem is the coolant temp sensor since it's temperature related. Any idea's at all?

 

[Mustang Ricky]

i believe the ECT sensor can affect the cold idle. something to look at. have you pulled the codes from the computer yet? you might want to that first. if nothing else, it get this thread back up to the top.

 

[Rieman]

I replace the coolant temp sensor and that didn't help. The problem is weird how sometimes the idle will stick at 1500rpm's and I can drive without any gas and I will pullup to a stop and the idle will suddendly raise up so I will have to shut the car off and restart it to get the idle back down. If I unplug the iac which again is brand new I don't have this problem. I have to sell this car asap and need to get this solved. I will check for codes even though the last time I checked for codes I got none and still had this problem. This is driving me crazy. I've spent $100 on two sensors and no fix.

 

[stock SVT]

Almost sounds more vacuum then sensor. Check all the connections. Did you do any motor work before this started?

 

[Rieman]

There is a hissing sound coming somewhere from the intake I believe. However I have hooked up a vacuum gauge and it stays steady and also have tried spraying carburetor cleaner around and can't find anything. The hissing is on and off again. The only work around the motor I have ever done is remove the upper intake. All the vacuum lines have been replaced.

 

[jerry beach]

Mine does the same thing now that the temps have dropped a bit. Its only for the first few minutes of driving so it doesnt bother me at all, really. If it was an automatic, it would bother me. What year is this car? Have you tried cleaning the MAF sensor? Clean the ACT sensor also. What does your vacuum guage read? It can be steady and still have a vac. leak. Mine has no vac. leak, and its doing it, just not as bad in the summer.