C200k Rough Idle (hot) + Errors: P0171 P0301 P0302 P0303 P0304

[NatD]

Hi All, have issue with poorly C200k, auto. Car has done 80k and is due a service.

Starts fine every time hot or cold. But when engine warm/hot the idle often (but not always) goes rough, very rough and the car drives terrible under 2000 rpm.

If you rev it between 1000-2000 rpm the car judders, splutters and shakes like mad, as if its only running on 2 cylinders.
Above 2000 rpm it seems ok again until you come to a stop and the idle is jumping all over the place like it’s going to stall (hasn't yet). Engine light is on so I borrowed an ODBII reader:

ODBII Errors:
P0171 - System too lean (Bank1)
P0301 - Missfire Cylinder 1
P0302 - Missfire Cylinder 2
P0303 - Missfire Cylinder 3
P0304 - Missfire Cylinder 4

I cleared the codes and tested over a few days. I get various combinations of these errors back if I drive the car for 20mins+.
The most consistent code is P0171 too lean but often there is more than just the one.
I know there are various posts on forum like this but none of them ever have a successful conclusion ( that is written up on the site. Perhaps this can be the first, fingers crossed!

So I have started work...

ACTION1: Checked then replaced plugs with like for like BOSH Iridium’s.
RESULT: No difference, error codes still pop up

ACTION2: Replace air filter.
RESULT: Car feels sharper to accelerate and more responsive. Initially was hopeful, but no, errors still appear.

ACTION3: Purchased some MAF cleaner... but not used it yet (job for tomorrow)
RESULT: TBC

Clean MAF, job for tomorrow. Looks a little awkward to remove but should be fine. Reinstall and test.
If the MAF clean didn't work I was going to replace the fuel filter. It’s cheap and looks an OK job to complete. I have run it very low (zero miles left on clock) a couple of times, but I have never 'run out' to a stop.

THEN WHAT?
Assuming I do the above and I still have the issue what else should I be looking at next? (Apart from going to my local MB 'Stealers')

Would really appreciate any advice / comments / suggestions as I think I will be pulling my hair out if I can’t solve it this weekend…..

Thanks
NatD

 

[Cole@MBS]

Get the vacuum pipes checked above and under the supercharger, probably find there fallen apart...
..

 

[NatD]

good shout, yes thank you. I was thinking of getting a couple anyway when I have the airbox & MAF off to clean it. I have read there is one there that often fails.

Question, do I need to go to MB for these or are they available from Eurocarparts / GSF etc?

 

[Cole@MBS]

MB only.......

 

[NatD]

UPDATE >>

Today driving to work I noticed the following with ODBII connected:

Cold Start on steady idle MAF reads a constant 4.5 g/s (+/- 0.3 variation)
When HOT with steady on idle MAF sensor reads 0 g/s
When HOT and idle starts jumping around MAF reading 0.0 - 4 g/s (varying)

Questions>

Is 0 g/s right when warm on steady idle or is this a sign the MAF is dirty / faulty? Or is this symptomatic of vacuum leak in system letting air in else where?

When idle is jumping around all over the place (reading 0.0 - 4 g/s), again does this symptom point to dirty / faulty MAF which is causing the erratic idle, or is the erratic MAF reading as a result of the erratic idle, caused my something else? (blocked fuel filter or vacuum leak?)

Many Thanks, just trying to narrow down and prioritise my actions for the weekend!

 

[triharas]

hello sir. did you fixed the problem somehow? i own a mercedes slk200 r171 163ps with errors p0171 p0301 p0302. please answer me if you could.