Rpms
- Thread starter 2vjordy
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Check for trouble codes. Consider stuck open Idle Air Control, or Throttle Plate (less likely). imp
wmburns
SN Certified Technician
+1 on above.
To add, how about a common garden variety vacuum leak? Or bad IAC valve?
Here's some more information on how to trouble shoot.
Troubleshoot IAC idle problems 1996-2004
https://www.stangnet.com/mustang-forums/resources/troubleshoot-iac-idle-problems-1996-2004.13/
It might be handy to mention the model year of your Mustang. But likely this won't change the trouble shooting steps.
To add, how about a common garden variety vacuum leak? Or bad IAC valve?
Here's some more information on how to trouble shoot.
Troubleshoot IAC idle problems 1996-2004
https://www.stangnet.com/mustang-forums/resources/troubleshoot-iac-idle-problems-1996-2004.13/
It might be handy to mention the model year of your Mustang. But likely this won't change the trouble shooting steps.
I changed the iac and the idle is going back down now but when I drive and come to stop the rpms still wanna stay up for like 15 sec then goes down..do I have to do a idle re learn process or something ? Or was the valve not the fix I mean before I put the valve the rpms wouldn't go down at all now they do just takes like 15 sec
Starting to think vacuum leak some where, which PCM is still able to "overcome" in efforts to reach idle speed. imp
wmburns
SN Certified Technician
Does the car's speedometer work? Why does this matter? Because it is NORMAL for the PCM to keep the idle slightly higher while the car is moving. The PCM will only select slow idle when the car is stopped.
Search on hanging idle as 1,000's have complained about it. The trick here is to understand the difference between a normal hanging idle and an abnormal hanging idle.
A 2,000 RPM idle isn't likely normal.
A 1200-1500 RPM idle while moving is normal.
Bottom line: IF the RPM eventually settles down to a normal slow idle that means that the IAC is working and is being commanded by the PCM.
Did you review any of the information provided in the trouble shooting IAC/idle link? Did you perform the IAC basic functionality test?
Regarding the relearning process. Is the battery and alternator in tip top shape? Have you driven the car for several days? If both are true then a working PCM has had more than enough time to re-learn.
I haven't driven it for several days yet and the idle is still high like that when not moving at all and even when coming to a stop sign or red light it's never stayed that high before
wmburns
SN Certified Technician
Here's some information on an affordable Windows based ODB2 scanner. How can this help? With an ODB2 scanner it's possible to monitor the IAC duty cycle. A slight vacuum leak will show up as a lower than normal IAC duty cycle.
ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/
Or course having an ODB2 scanner will open up a world of other diagnostic information. Car repair will never be the same after you see what an ODB2 scanner really can do.
ForScan ODB2 scanner w ELM327 USB
https://www.stangnet.com/mustang-forums/resources/forscan-odb2-scanner-w-elm327-usb.57/
Or course having an ODB2 scanner will open up a world of other diagnostic information. Car repair will never be the same after you see what an ODB2 scanner really can do.
