Heres a random question of curiosity... I'm sure other people have noticed this on their cars: when your car's idling at a red light or just in general, sometimes the rpms's drop a few 100rpms, and then after a couple seconds raise back up to regular idling rpm's.... I was just wondering, if anyone knew the reason for this? My Evo has cams (272/272), but my BMW 540i is all stock and does the same drop and raise as well... Any clue?

Jason

 

I think thats from the fans or ac compressor turning on. I believe it causes a loss of momentary power.

 

Accessories turning on and off along with idle speed control. Usually A/C as EriCS said.

 

Happens to me all the time

 

+1

 

Ahh, thanks! i assumed it was something to do with AC and belt, when you increase your AC to 4 or so, the idles raise as well, thanks for the thoughts, curiosity cured!