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W203 C180K misfire

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by Tomkinsm, May 9, 2018.

  1. Tomkinsm

    Tomkinsm Senior Member

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    Hi all,

    My W203 C180K has started to misfire on start-up. It's been happening, occasionally, for a few months, but now becoming more regular. It will misfire and run lumpy, I turn it off and restart and it runs fine. Once going, it seems to run fine as normal. It throws up the engine management light sometimes, but not always. The most recent codes I read using a generic reader are:
    P0303 cylinder 3 misfire detected
    P0302 cylinder 2 misfire detected
    P0172 system too rich (bank 1)

    I replaced the plugs, air filter and fuel filter. It didn't fix the problem.

    I wonder if it's a coil pack issue, or something more complex. I realise this could be many things, but if anyone has some suggestions it would be helpful and much appreciated.

    Thanks
     
  2. Diddles

    Diddles Senior Member

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    Your Mercedes:
    C class 2007 1.8
    Could be crank case ventilation hoses split. Does the engine hunt when cold?
     
  3. OP
    Tomkinsm

    Tomkinsm Senior Member

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    Sometimes, but not often. But it's a good suggestion, I'll check the hoses, thanks.
     
  4. OP
    Tomkinsm

    Tomkinsm Senior Member

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    Finally got around to looking at this. The crankcase ventilation hose was indeed split. Not a nice job but I managed to change it and felt optimistic I'd solved it....

    But car is still not right. Exhaust smells rich and takes a long time to start when hot. Cold start is fine and car seems to drive ok though.

    Any other ideas? I wonder if I should have changed the MAF when I had the airbox off.
     
  5. Oldspanners

    Oldspanners Senior Member

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    Your Mercedes:
    C CLASS 2004 C180
    It may take a while to re
    It may take a while to re-learn the new settings.
    Was there a lot of oil in the intake?
    Other problems may be the O2 sensors but that will throw up codes.
    Oil leaking into the wiring harness if blockers haven't been fitted at the cam magnets.
    Cam chain and sprockets worn.
     
  6. Diddles

    Diddles Senior Member

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    Your Mercedes:
    C class 2007 1.8
    20180428_134204.jpg That top crank case ventilation pipe does go into a valve and then another pipe which also fail and split.

    They are harder to get to, I did mine while I had the head off so was easy, but normally it's intake manifold off and kompressor out the way.
     
  7. OP
    Tomkinsm

    Tomkinsm Senior Member

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    Thanks for suggestions.

    There was some oil in the pipe between the airbox and the compressor but the inside of the elbow of the airbox looked dry.

    Yes I read about the valve and the second pipe. I think that job is beyond me...at least I don't have the time.

    It's almost as if the car thinks it's cold and applies a choke or rich mixture even when hot. Cold start is perfect. Temperature sensor looks ok though, engine temp on display seems normal. I guess I need to get a proper diagnosis, my generic OBD reader is probably a bit limited.

    Any idea how long (or miles) it takes to re-learn?
     
  8. Oldspanners

    Oldspanners Senior Member

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    Your Mercedes:
    C CLASS 2004 C180
    With mine it varied depending on what sort of journeys I did, long, short, fast, slow. On the OBD reader I have it will show when all sensors are back on line either by a LED changing from orange to green (or red if the problem re-occurs) or by reading their state.
    The problem I had was oil wicking into the wiring harness and putting the after cat o2 sensor off line but it certainly made the mixture rich reflected in the exhaust and obviously MPG.
     
  9. OP
    Tomkinsm

    Tomkinsm Senior Member

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    How about the intake air temp sensor - I assume there is one? Would explain why it's only happening when hot.

    Can anyone tell me where it is please?
     
  10. LostKiwi

    LostKiwi Senior Member

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    Your Mercedes:
    '93 500SL-32, '01 W210 Estate E240, 02 R230 SL500 (Malcolm Spec), 04 Smart Roadster Coupe
    If you have live data on your code reader it should be able to show the IAT.
     
  11. OP
    Tomkinsm

    Tomkinsm Senior Member

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    It's now nearly a week since I changed the PCV hose and the good news is that I've had no misfires and there are no fault codes coming up. So I think thats solved at least the initial P0172 and misfires.

    ...But the engine is still taking a long time to start when hot. It never fails to start, but cranks over a lot before firing. IAT and engine temps all look normal on the code reader.

    I found a number of reports of other engines with hot stating issues where people pointed towards the crankshaft position sensor. Would this also cause a hot starting issue on the M271 engine?
     
  12. LostKiwi

    LostKiwi Senior Member

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    Your Mercedes:
    '93 500SL-32, '01 W210 Estate E240, 02 R230 SL500 (Malcolm Spec), 04 Smart Roadster Coupe
    CPS failures usually mean no start when hot.
     

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