Idling issues E320 1997 W210
I have never experienced this issue before. The car has relatively new spark plugs and spark plug wires (changed a couple of years ago), changed also two of the three dual coils and cleaned the Mass Air Flow Sensor about two years ago too.
I usually put only about 4,000 miles a year on this car.
The issue only happens at idle. I don't have the "Check Engine" light on at all.
Does any one has an idea/suggestions where should I start to troubleshoot?
I´d appreciate very much your ideas.
Thanks!
Last edited by Klrgator; Jul 12, 2018 at 12:36 PM.




When bad CPS will not show error on this car - bad PPS will trigger CEL and that error happens usually when you floor it. Meaning you can eliminate that one as well.
Still you should always start troubleshooting with code reading (even when there is a chance you might not have them).
Your car require 38-pin scanner plug for full reading, but even with standard OBD you might get something.
Thanks for your answer.
I have the M104 engine (six cylinder in line) and not the M112.
This is a strange issue since the car runs perfect at any RPM above idle.
The temperature is being reported properly.
I have a friend with an ODB scanner. I´ll plug it in and read any codes that may happen. I did use this scanner in the past and helped me to solve a "Check engine" light (issue with the cam positioning sensor) so I´ll give it a try.
I´ll also check for any possible "false air intake" between the air filter and the intake of the engine.
I will update my findings.
Thanks again!!!
After driving the car for several days and having this fiddling issue, the problem started to become more noticeable at all speeds until a Check Engine light came on.
I got a "P0306 Generic Code Cylinder 6 Misfire Detected". Based on this I checked the spark plug (which was changed when I changed all the spark plug cables), as well as the condition of the rubber plugs that are attached to the ignition coil that fires cylinder 6.
After all these tested OK, I replaced the ignition coil that controls cylinder 6 and cylinder one (this car model uses one coil for every two cylinders) and the problem got away!!!
Thanks everybody for your comments and help!!
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