fleishman

Hello all,

My '02 c32 w/ 120K mi. usually runs mint every day however I pulled out of the driveway this morning and the idle started to surge/bounce and I had to pull right back in. Upon restart the idle would jump up a little higher than normal (2K) and drop to a little higher than normal (.9K). As soon as I even tapped the throttle it would jump to 1.2K and bounce rhythmically between 1.2-1.5k and the engine did not sound too happy; felt bucky and lots of exhaust noise. No codes.

From my experience with crappy American cars I looked to the throttle body area MAF, IAC etc. I took the intake off and checked TB plug connections, butterfly movement, looked for deposits etc. There was a little bit of oil residue on the inside of the TB.

I reset the TB, the ECU etc and this thread was extremely helpful: https://mbworld.org/forums/c32-amg-c55-amg-w203/451878-ruh-roh-raggy-p0120.html?highlight=p0120

After all that messing around there was no change in symptoms but it did throw a p0120 (TB malfunction) and p0105 (Map sensor). I don't know if that was due my several reset attempts with varying methods or just giving it more time to run and log errors.

Searching for similar symptoms in the forums and google I came up with only expensive visits to a STAR station or new throttle parts.

Guess what, a few squirts of carb cleaner at idle and the symptoms stopped immediately and have not returned! I do have a homemade aftermarket intake but don't have oiled filters. Way less oil blow by and dust is getting by my set up than I saw when I took apart the factory boxes. I think this should be anyone's back to basics first approach to this fault.

Any input out there? Should I be sourcing a TB because this will return?

I searched but have not found an instructional on how to properly clean the TB and MAF, if anyone has one please post. Seafoam next weekend for sure!

60n5pt1

I've been having this idle surge for awhile now,too. I've disconnected the throttle body connector and cleaned it with electrical cleaner spray. Not much changed, if anything, probably made things a bit worse.
This morning I went for a smog test and guess what..FAILED..but not because of emissions but, rather due to smog equipment could not read
ECU or something else. Smog guy says battery must have been disconnected
or a diagnostic test was done previously. None of which has happened in the last 3 years. He syas drive around about 100 miles or so and then come back and he'll test again. I'm not sure that's going to change or fix anything.
He must be thinking of resetting or clearing CEL codes which none have come up on screen.

This idle surge and engine rpm going up and down at idle is really annoying.

evilsaint

Check out the torque on your header bolts, for leaky valve covers, and for vacuum leaks on the hose that hooks up to the bottom of your TB. That hose was the main issue with mine.

If you want to replace the stock wiring to your TB on the cheap, you can get the genuine Mercedes part right here - wiring between the TB actuator and the connector further down the line toward the engine wiring harnesss.