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SLK200 R171 2005 IGNITION COIL.

Discussion in 'Electrics, Vacuum, Ignition and ECU' started by bobster1, Dec 23, 2012.

  1. bobster1

    bobster1 Active Member

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    Hi,
    been having probs for while with misfire and stuttering, had codes taken and shows P201A misfire on cylinder #4. I have changed the spark plugs last week, so i am thinking coil pack or wiring. is this reasonable?? I intend to change coil, is cyl #4 nearest the windscreen?

    any thoughts?? thanks

    bob
     
  2. television

    television Always remembered RIP

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    The coil packs can fail on this engine some swap them around to prove the point but it should be just that one ;)
     
  3. Alex Crow

    Alex Crow Senior Member

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    Yes, worth a try, and no.4 is at the back near the screen.

    Sadly the common issue with these is poor valve seating, giving rise to missfiring.
     
  4. television

    television Always remembered RIP

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    Is it the 271 where the valve seats can crack Alex
     
  5. OP
    bobster1

    bobster1 Active Member

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    Thanks for your replies . Hope it is the coil

    Is the valve problem a big job for an indie?
     
  6. television

    television Always remembered RIP

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    I am sure now that Alex mentioned it that it is a valve seat that splits and the head was re designed, so a new head if that was the case.

    I do have details somewhere saying which number they split on
     
  7. television

    television Always remembered RIP

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    Alex was right (always right) when he mentioned the valves, it is the exhaust valve seats that wear, also the valves can become spotted, but no cylinder number mentioned
     
  8. OP
    bobster1

    bobster1 Active Member

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    Thanks again. The car only seems to misfire when at normal temp runs well when cold. Idle is normal. Removed all plugs today they also look normal. No noises from engine. I would have expected more symptoms if valve was problem.
     
  9. Alex Crow

    Alex Crow Senior Member

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    No, your symptoms fit nicely.

    Remember, what you have is a sensitive engine management system, that can detect a slight loss of compression (via crank position signal).
    If it took no action, you might not even notice the slight uneven running. However, as a protective measure it will shut down a cylinder (ie not inject fuel) to prevent the possibility of overheating a cat. This you will notice, as it will only be running on 3x cylinders until it resets (eg ignition turned off).

    A compression test when hot would be a good way forward.
     
    Last edited: Dec 24, 2012
  10. OP
    bobster1

    bobster1 Active Member

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    Thanks Alex Got a new coil today And fitted it 90% better but still a very occasional stutter a lot better but not perfect.
    I Am due a service in 1500 miles would you suggest running car till then or should I have checked. Urgently. In short if it is a valve issue is it dangerous to run
    Thanks
     
  11. television

    television Always remembered RIP

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    A valve issue is not dangerous if a seat worn, the compression will be down on that cylinder and you lose some power. The worst is that the head must be replaced
     
  12. Steve@Avantgarde

    Steve@Avantgarde Forum Supporter Authorised Forum Supporter

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    Alex is right regarding poor valve seating on the 271 engine but it was mainly sorted out by the time it went into the W171. It was the 2003/2004 that gave rise to most of the valve seat issues and most if not all had modified heads by late 2004.

    The stretched timing chain issue will also cause a misfire and uncharacteristic running issues and almost a dead cert to affect a W171. Maybe this is the issue.
     
  13. OP
    bobster1

    bobster1 Active Member

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    Thanks for your replies. Is there a test for a streatched timing chain that an indie can do? What is the fix if it is the chain is there a tensioner? If so how many possible hours labour involved. I can also get compression test carried out. Thanks
     
    Last edited: Dec 27, 2012
  14. television

    television Always remembered RIP

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    You set the crankshaft timing marks up on the flywheel at the front of the engine, the rocker cover must be removed and then check the timing marks on the cam sprockets.

    When setting up the timing marks on the flywheel, best to remove the sparking plugs, and you only turn the engine clockwise, if you over shoot, the you must turn the engine back at least a ⅓rd and turn again till the marks come up in line with the pointer.
     
  15. OP
    bobster1

    bobster1 Active Member

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    Thanks for that. I am intending to take car to indie for these checks to be done. I don't have any engine rattle or noise just this stutter when warm. I am a bit paranoid now and am avoiding using the car. Is there a danger I could damage car further by using. For an indie what kind of labour hours should they need to diagnose problems
     
  16. television

    television Always remembered RIP

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    I just cannot advise you to use the car or not :D most indies are about £40-60 per hour, there again one might be able to pin point the problem very quickly.
     
  17. OP
    bobster1

    bobster1 Active Member

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    Alex. Is it worth swapping the injectors on cyl 4. Code seems to point to injector faulty or wiring. I had fuel pump changed 6months ago after failure having checked indie job receipt I don't think the filter was changed, was thinking maybe debris in tank fouling injector??
    Thanks
     
  18. drdre78

    drdre78 Senior Member

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    hi just swap coil number 4 with number 3 and see if fault moves.while you checking check vacuum pipes under airbox which usally start of lot of problems
     
  19. Steve@Avantgarde

    Steve@Avantgarde Forum Supporter Authorised Forum Supporter

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    There is a lot of guessing going on by the op and not much in the way of diagnosis. Alex and myself have highlighted the potential running issues of the 271. What is needed now is solid diagnosis.

    What needs to be done now is STAR diagnosis test, check vacuum pipe for splits, compression test and then check the timing if nothing shows in the first 3.

    Until you have done those 3 tests you are proverbially peeing in the wind!!

    There is highly unlikely to be anything wrong with the injectors like it was highly unlikely to be your coil pack causing the issue. This is the most time consuming and expensive way to attempt to fix this fault and I would recommend you get it to an Indie to help.

    And Malc is right, the more you drive it the more there is a potential problem for bigger failure, especially if it is a stretched chain.
     
    Last edited: Dec 29, 2012
  20. OP
    bobster1

    bobster1 Active Member

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    Thanks Steve Yes have booked car in to indie but he can't look till After new year, just pottering today in case there was something more I could do.
     

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