300SDL stutter/shudder at idle - PeachParts Mercedes-Benz Forum

boblo_home · #1 08-30-2010, 12:53 PM

So here is my situation. 334K on the clock with no issues before.

The problem is when the car is at idle. It will be real smooth and then you get a sort of roll in the engine…the whole car does a shudder. It can be fine for a few minute or more before it shudders. Sometimes it will do this just once and other times it will sort of repeat itself like a stutter.

I did this test. When the car is cold in the morning it will start at the first spin and idle smooth. I left the car idling for 5 minutes and then it would shudder/stutter. Smoke would be coming out from the vent hole at the back of the valve cover. I stepped on the pedal and then it will smooth out. The shudder can be slight or cause the whole car to shake. It is very annoying when it is at the stop light. After driven the car for a while then it would not happen again, not I am aware of anyway.

Car has a lot of power and get good gas mileage. All the filters have been changed, oil changed and compression in the 320+ range across all cylinders.

Any idea what could be wrong?

MattBelliveau · #2 08-30-2010, 01:53 PM

Injectors? Does anyone else know of a rack pin on this engine?

boblo_home · #3 09-01-2010, 10:52 AM

Any other suggestions that I can check?

BoiseBenz · #4 09-01-2010, 02:04 PM

Something is goofy with your crankcase venting system. It's building pressure, which causes the vent to vent AND allegedly activates the shutdown diaphragm.