97 C 230, low RPM violent shuddering and CEL - PeachParts Mercedes-Benz Forum

Will_w202 · #1 02-28-2005, 07:49 PM

So the car was running a little rough tonight, and then I finally got a check engine light, and it would barely move from a standing start. When I would start off, it felt like it was running on 2 cylinders. Once up to about 2000 RPM or so, it smoothed out. So I drove home in 3rd gear. It just so happens I have an appointment for an oil change in the morning. Good timing. The car has Starmark warranty. Any ideas? I first thought MAF sensor, but I don't recall any of my VWs being rough when a MAF died, just slowwww.

Ethan · #2 02-28-2005, 08:26 PM

Could be MAA sensor, ask them at the dealer to read you the codes they pull. Then come back here with the codes and the fix they recommended.

Could be your ignition high-tension wires are kaput.

Also - a liitle tip that may or may not reveal the problem - when it happens check your tach. If the tachometer falls to zero instantaneously electrical problem, If the tachometer reacts, if it reacts at all, by dropping incrementally it is a fuel delivery problem.

Will_w202 · #3 02-28-2005, 08:53 PM

Thanks Ethan,

Tach didn't jump. One thing I should note is that it had been raining all night and day before this happened. Whether it's related or not I do not know, but I thought of it when you mentioned ignition wires.

Will_w202 · #4 03-01-2005, 12:11 PM

So my hunch was right, that the all-day cold rain yesterday unveiled a problem. Codes PO300 and PO302 were found, misfires for cyl#2, fuel pressure ok at 3.0-3.5 bar. The tech notes say "severe carbon tracking found on spark plugs and resistor tips." There must have been some corrosion or open point somewhere allowing moisture in. They charged me for plugs and labor, and as the car was nearly undriveable, I wasn't going to take it home and fool with it today myself. Resisitor tips were covered under warranty. Now, the plugs should have been replaced at 60k service, which they did before I bought it, and if that is the case, I can't believe they went with 20k on them! Maybe bad resistor tips could kill them?

Ethan · #5 03-01-2005, 02:54 PM

I doubt the dealer did the 60K plug service as they claim.
I am even curious if they could have been the original plugs. For moisture to cause such resistance problems, the material had to be shot, similar to what would happen in 80K miles.

Goes to show always a good idea to get old parts back when having new ones installed.

Will_w202 · #6 03-01-2005, 03:10 PM

Oh I would think they had to be original. I was pressed for time today, but I plan to research it further, and if they did not get replaced at 60k, I'm going to shoot for a couple of free oil changes.

EDIT - I just called my rep, and she said they were changed at the 60k service, which was done 3k before I bought the car, at 61k. Must have been some nasty resistor tips, yikes.