w202 1999 c240 schematic diagram of the engine wiring

[alfhoc]

Good day all, I have an intermittent fault that causes the motor to run very rough at low revs. Above 2000 rpm it runs as normal.Any help will be appreciated

 

[mbenz1]

You should get it checked on STAR first to see what fault comes up and then proceed accordingly. Some general problems with this engine are the MAF sensor failing, wrong spark plugs, faulty plug leads (which I suspect is the problem in my CLK320) and coil packs. But a STAR check should direct you to the right solution.

 

[alfhoc]

Hi the STAR check just indicates that the motor is missing on 1, 3, 6 cylinders. The MB DEALER service station dont have a clue because their system keeps indicating that different cylinders have a miss. SO now I dont know.

 

[andy27168]

Hi,
If you are positive you haven't got an issue with the ignition system then I think I would be looking at a possible air leak.
If the car were mine I would check the pipes are clear and intact that come off the back of the rocker covers and go to the large plastic elbow shaped pipe under the MAF, and remove the throttle body and replace the O ring seals either side of it, and give the throttle body a good clean with carburettor cleaner while its off.
I also can,t help but wonder if there is possibly a fuel pressure issue, as there is a vacuum operated valve on the fuel rail if this wasn't operating correctly/sticking might cause slow running issues and as it is vacuum operated when the rpm rises the increased vacuum frees it, just a thought.