M112 - rough idle
Junior Member
Joined: Jun 2013
Posts: 19
Likes: 2
2002 CLK55
Few thoughts here - firstly I would stay away from 100 octane as it's only going to put strain on your knock sensors (cold even be the issue). I would also say try using a difference code reader. I own 3 of them and I can tell you that I have had instances where each pulled a code that the other didn't at some point. Amazingly my oldest (15yr) OBD-II reader is the most consistent.
Some possibilities could include: do this first > ignition coils (unclip and reattach them...I had broke one without realizing it after I did my valve gaskets), gas cap, motor mounts, knock sensor, fouled spark plugs...
Some possibilities could include: do this first > ignition coils (unclip and reattach them...I had broke one without realizing it after I did my valve gaskets), gas cap, motor mounts, knock sensor, fouled spark plugs...
Junior Member
Joined: Feb 2018
Posts: 22
Likes: 1
From: Tucson, AZ
1978 300CD, 1985 300SD, 2002 CLK430 Cabrio
100 octane fuel?!?! Holy Schmokes! That's aviation grade around these parts! Unless your vehicle is utilizing some form of forced induction or you are running some crazy ignition advance, you do not need anywhere near that level of octane!
Still, that doesn't explain the rough running and the difference between colors of the metal valve-train parts on the cylinder heads. That is odd indeed! I will be interested to learn what you finally discover is the culprit behind that.
Still, that doesn't explain the rough running and the difference between colors of the metal valve-train parts on the cylinder heads. That is odd indeed! I will be interested to learn what you finally discover is the culprit behind that.
MBWorld Fanatic!
Joined: Jul 2012
Posts: 1,254
Likes: 171
2002 CL500 to CL55 conversion
Wanted to follow up on this thread
thought I blew a valve or piston rings after installing a turbo on my 55 engine swapped w215 car. I’ve definitely been pushing the car hard
ran great at first, now I’m getting an annoying rough idle and maybe only 80% power but no check engine light.
an in depth engine idle monitor in Star diagnostics reveals faults on cylinder one. I swapped ignition coils, tested compression, swapped spark plugs and tested ignition wires. Running out of things to test besides getting the wiring diagrams out
thought I blew a valve or piston rings after installing a turbo on my 55 engine swapped w215 car. I’ve definitely been pushing the car hard
ran great at first, now I’m getting an annoying rough idle and maybe only 80% power but no check engine light.
an in depth engine idle monitor in Star diagnostics reveals faults on cylinder one. I swapped ignition coils, tested compression, swapped spark plugs and tested ignition wires. Running out of things to test besides getting the wiring diagrams out
