Having issues at idleing

[brdh24]

So my 98 2500 Cheyenne has started doing something it had never done while in idle, it will randomly start revving on its own without any movement of the throttle. It will go to about 1500 rpm, slow back to normal idle, then spike again, with 0 input from me. While it’s randomly happening, I’ve noticed it mainly occurs when stopped at a light, or, when shifting from park into gear, both reverse and drive. Does anyone know what could be causing this? The only thing I can think of is the cold air filter I put on it is maybe confusing the MAF and the computer is getting a wrong reading? However I’ve had the filter since late March and haven’t had this problem until recently, it also isn’t doing it at all when going down the road, or revving it in park, only while the engine is idleing. Any ideas?

 

[funnyfarm]

Has the check engine light come on if so see if there is a throttle positioning sensor or a manifold air pressure or your mass air flow sensor causing that. More than likely it is your IAC sensor. Now if you have no check engine light on and no codes I would then start looking towards mechanical things like do you have a dirty mass air flow sensor is the butterfly on the throttle body dirty or gunked up possible small vacuum leak will increase her RPM also there's a few different number of things but that's where I would start.

 

[Schurkey]

Very likely a problem with the IAC or the IAC control circuitry/logic.

Connect a scan tool, find out what the computer wants you to know.