C240 idle going nuts!
 

So today I was driving my 01 C240 with 90k - kms and as I waited at a light the idle decides to drop and then rise to 2000rpm almost causing me to drive into the middle of the intersection. I got really scared and parked it back at home.

What could be the cause of this?

Could be the gas pedal OR the throttle actuator sticking...ANY check engine lamp?

No check engine or messages. This happened while holding the brake. The throttle on this car uses no cables eitheir.

The gas pedal has a potentiometer that could be sending an errant signal w/o causing a check engine lamp OR the actual throttle butterfly could be hanging-up on a carbon build-up.

i have seen some have similar issues when there is excessive carbon, try cleaning the unit and see how it goes, once it is clened leave the key on for 3-4 minutes so as to learn the throttle angle

I'd recommend checking to see if the air filter is properly fitted to the MAF sensor. If it's worked it's way loose, or was installed incorrectly, the engine will breathe in very hot, unfiltered air from under the hood as soon as the vehicle comes to a stop. The sudden change in temperature throws the fuel trim out of whack, causing the problem you describe. I've seen this happen many times.

Hmm possibly it is carbon. It is mostly city driven by my mother...it is being checked out today.