[SOLVED] Engine backfire. Please help!

Discussion in 'Engine' started by c200_impressor, Mar 8, 2011.

  1. c200_impressor

    c200_impressor New Member

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    Hi. I need some advice...

    My C200 1998 W202 (manual) is backfiring intermittently and 'hesitates' under acceleration... especially when accelerating in 3rd gear.

    I've put in new spark plugs, new air filter, new ignition leads and new ignition coils but the problem remains.

    I've no idea what else could be causing the problem?!

    Engine ECU maybe?

    Any ideas anyone???
     
  2. Stratman

    Stratman Hardcore MB Enthusiast

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    Welcome to the forums, sorry it's under such circumstances.

    The crankshaft position sensor sound a likely culprit.
     
  3. grober

    grober MB Club Veteran

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    Sounds like the mixture is off. So could be the MAFF or maybe the Lambda sensor/s
     
  4. OP
    OP
    c200_impressor

    c200_impressor New Member

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    Thanks for the replies guys.

    Will an ECU test tell me if it's the maff/lambda/crankshaft sensors?

    Or will I just have to replace them all??
     
  5. BlackC55

    BlackC55 Authorised Forum Sponsor Authorised Forum Sponsor

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    I would say the MAF is at fault. Get the live data and fault codes checked first.
     
  6. OP
    OP
    c200_impressor

    c200_impressor New Member

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    Thanks. How do I go about checking the live data & fault codes?
     
  7. GordonTarling

    GordonTarling Hardcore MB Enthusiast

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    You take it to someone who knows what they're doing, like Olly (BlackC55), with a STAR machine.
     
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  8. BlackC55

    BlackC55 Authorised Forum Sponsor Authorised Forum Sponsor

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    With a diagnosstic machine. Your local specialist or dealer has such equipment.
     
  9. Dieselman

    Dieselman Banned

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    You can check the MAF with a voltmeter attached to Pin-5 and Gnd. Expect ~2v at idle rising to ~4.8 at full revs.

    The fault does sound like the MAF may be causing a weak mixture so spitting back.
     
  10. horgantrevor

    horgantrevor Hardcore MB Enthusiast

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    hi i would also say maf

    open bonnet and unplug the maf its located on the pipe from the air box to engine

    if you keep driving with a backfire this means your dumping unburned fuel into exhaust and you will reck your cat
     
  11. OP
    OP
    c200_impressor

    c200_impressor New Member

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    Mega thanks to everyone for the help. Much appreciated!!!!

    Looks like it's definately the MAF because when I unplug it the engine runs perfectly and is back to full power. Only problem is it causes the cooling fan to be on permenantly even when cold which is a bit odd. Will source a new MAF asap.

    Cheers again people!
     
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