Well I Notice it every once and awhile on my stang, I'll be sitting and my car will be idling at about 700RPMS and it will start going up and down in rpms Like from 500-1000 and back to 700...seems like its surging or something...did it to me tonight in rush hour traffic on the freeway and my car actually stalled...very weird...

do you guys know what causes it?

 

yea but not to that extent

might wana get it checked out

 

Possible cloggd catalyc converters. Get it checkd and u can unclog em yourself.

 

Mine does a little but not as much as yours is.

 

Sounds like your radiator fan is turning on. It does this after running it for a while.

 

i mean that might be it...doesn't sound like the engine has anything wrong with it, it still runs great, just sometimes it fluctuates a bit....and it might of just dropped too low of rpms to pick itself back up earlier...

 

when the A/C compressor cycles on and off, but usually in idle, and not to the point of dying on me.

 

80% chance it's your idel air control valve
10% chance it's your EGR system
5% chance it's a dirty MAF sensor
5% chance it's something else sensor/eletrical wise

 

+1 on checking the IAC

 

where is the idle air control valve?