hi All, please help me.. I am really confused and need some ideas as to where to look for a weird issue that I am having with my 2004 E200 Kompressor (M271 Engine). My car has 43K miles and has the 4 cylinder engine (M271, Which is like a W203)

The morning start is a little rough on some mornings (If i didn't start the car 24 hours or left the car sitting 2 days), ie you start the car and for the first 30 secs she runs rough and a little bit misfires. then it clears and the motor smooths off and all is ok. this is intermittent, ie might happen once or twice a week.

Then when the car is on the road everything feels ok, motor responds well, just like a normal day. then, also intermittently, the car will stat to misfire when you come to a stop or idle. it feels as if she is only running on 3 cylinders.

there is no CEL/warning apart from a slight vibration coming from engine, and then suddenly will start the misfire.
you can be in full and proper town stop start driving with no problems, and then this will suddenly kick in.
to clear the problem you turn the engine off, give it 5 secs and restart it and she runs properly.
the same issue might happen again, but then again turn off and restart and she runs properly.

This misfires is only at idle, when you kick the rpm the vibration is hardly to feel..

a point to note is that once she stats this it will carry on happening UNTIL the motor has been turned off and allowed to cool down, or until you get onto a long run.
the issue does not appear to be influenced by engine temp, it can happen when motor is at full running temp or even at 3/4 running temp.
apart from cold start as described above never happens when cold.

I have checked the following;

- compression all 4 cylinders (Normal)
- changed the fuel pump and the fuel filter 3 weeks ago (due to age)
- changed ALL spark plugs
- changed ALL the fuel injectors
- changed ALL Coils
- Changed the Legendary "$12 Hose" issue
- Running on 95 RON Gasoline (before i use 92 RON but since i replace the fuel pump & filters i managed to change fuel too)


Have had a Star diag done, and no error code comes up on display when the problem occurs.Is it possible a faulty MAF sensor? can it be cleaned? or maybe a o2 sensors? i dont know.. i'm just very confused...

note : At my local Mercedes dealer they said that MAF sensor Can't be clean although it can be cleaned but not going to solve the problem forever

I am very confused, sounds like possibly a fuel problem, but cannot find any reason for it...

any ideas... please HELP me guys your answer is very helpful to me.. thank you

 

I have the same problem with my 2004 E320 please we need help to fix this problem . thanks