Fluctuating idle when stopped but still in gear
7 Answers
A few common reason: a bad or dirty MAF sensor (use MAF cleaner only on it), a faulty idle air control valve or circuit, or a vacuum leak. For the MAF sensor try unplugging it and see if it changes symptoms. Most of the time you should have a OBD trouble code set with a bad MAF but you may be borderline. For a vacuum leak try spraying ether (aka starting fluid) in and around the intake with engine running, if the leak sucks in the ether you'll get a brief surge in engine RPM.
Is the ac running at the same time? And how much does it fluctuate? How many rpms?
It still does it whether the air cond. is on or off. From 500 50 1100 rpms.
in my experience, I would invest in some brake parts cleaner, disassemble the throttle body, throttle position sensor, and idle air valve and give them a good thorough cleaning. be liberal with the brake cleaner. Make it look like new. If you notice any corrosion especially in the idle air valve, replace it - part is cheap and you can DEFINITELY salvage one for between free and $5. Put it all back together and BAM! Also in my experience, doing this confuses the hell out of the computer and your idling will be extra weird for about a minute or two until the system re-calibrates to your throttle not being choked and it should settle down. Hope this helps/works!
^That job should take between an hour and an hour and a half, depending on your skill/confidence and how gunked up your throttle body is.
Have the tps and the idle air mixture sensors checked
