E430 slight misfire at idle

Discussion in 'Engine' started by lynall, Jul 31, 2008.

  1. lynall

    lynall Hardcore MB Enthusiast

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    Slight misfire at tickover runs fine rest of the time, doesnt do it straight away takes a couple of seconds once revs have dropped.

    Have serviced it all oils and filters spark plugs cleaned maf all to no avail.

    Plugs did not look very old, oil filthy as was air filter

    Any ideas appreciated



    Lynall
     
  2. c240yaz

    c240yaz Hardcore MB Enthusiast

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    Although I do not know what your tick over RPM should be, could it be too low ?

    Oils have nothing to do with misfires. (I am sure that you will know this)
     
    Last edited: Jul 31, 2008
  3. clegsr

    clegsr Hardcore MB Enthusiast

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    Has it always done it?
    I remember on my E430, occsionally when I take it in for a service the techs have commented that it misfires on idle but otherwise it seems fine to me - and never needed any work to fix it. so I live with it and as you can hardly hear the engine at idle anyway I dont bother with it.


    ...Its more fun when its not idling...
     
  4. alibally

    alibally Hardcore MB Enthusiast

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    Might be plug leads .. Problem is there are 16 as they are 2 plugs per cylinder.
     
  5. OP
    OP
    lynall

    lynall Hardcore MB Enthusiast

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    Ticks over at about 600rpm ish which i assume is right as its a bit of a lump.

    Trucks at work are about the same but the are 13 litre.

    As oil was filthy and they have hydraulic tappets i would assume that dirty contaminated oil could effect tappet operation and hence tickover.



    Lynall
     
  6. c240yaz

    c240yaz Hardcore MB Enthusiast

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    and they are about £25 per lead.
     
  7. OP
    OP
    lynall

    lynall Hardcore MB Enthusiast

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    Looks like i can live with the misfire until i get an obd tool.



    Lynall
     
  8. benztech

    benztech Member

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    People get fooled by this one.

    The path of diagnosis is if you have a fault with your spark plug, lead or coil pack then the star will show it as a misfire on the relevant cylinder

    Now if it is running slightly rough on idle feeling it on the body of the car then i would say it might be the EGR valve they stick slightly on older cars. or slight moisture in the fuel system that will never come out on its own but you will have to flush the system - moisture is naturally created in the tank and over a period of time will work its way up to the fuel injectors.

    A "star"diag will be confirmation and will save you alot of time and money and hassle.

    I have seen this many times - dealers still get fooled by this one.
     
  9. Dieselman

    Dieselman Banned

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    Will a dose of injector cleaner or isopropyl alchohol not fetch the water out.? Should do.
     
  10. benztech

    benztech Member

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    Ive used it on a CLK once and theres been no more problems since hes said it runs like a dream now. But it really depends id say to what extent its running rough or how much water is in it.
     
  11. OP
    OP
    lynall

    lynall Hardcore MB Enthusiast

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    I will remove and check the egr valve i didnt know it had one until i was changing the plugs and laying over the bonnet trying to get the drivers side rear cap back on then i saw it.

    Every diesel car i have ever owned the egr has been straight in the bin:)

    Any idea of what percentage i should dose the fuel at with isopropyl alchohol?

    Boots here we come;)

    Lynall
     
  12. Dieselman

    Dieselman Banned

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    A few capfulls should do, it attracts water so flushes it out.

    I wish binning the EGR was as easy on diesels equipped with a MAF sensor.:devil:
     
  13. OP
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    lynall

    lynall Hardcore MB Enthusiast

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    Dieselman thanks for the reply, ordered some today £5.50 for 500ml getting it tomorrow;) .



    Lynall
     
  14. OP
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    lynall

    lynall Hardcore MB Enthusiast

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    Right alcohol in the tank has made no difference.

    Egr valve removed and did not leak when filled with brake cleaner.

    Throttle body removed and all the oily gunge removed.

    Def sounds like a coil or lead to me, waiting for a mate to come around with his oscilliscope (spelt right?)

    Any idea of the tickover speed of the e430?



    Lynall
     
  15. DPUL

    DPUL New Member

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    Engine misfire.

    Hi, I had a similar problem with my 2003, C 200 K, checked plugs, coils, replaced hoses and still had the problem. Diagnostic machine kept coming up with unidentified problem. Cylinder head was removed and found excessive play in one of the valve guides caused the valve to damage the valve seat. When the engine stopped the valve reseated and because of this, didn't show up on compression test. Had to have new cylinder head which cost just over £3000 with fitting.

    DPUL
     
    Last edited: Aug 16, 2008
  16. Uberwagon

    Uberwagon Hardcore MB Enthusiast

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    I had similar symptoms to you after a hard run, it didn't happen as much when I used V-Power and then what fixed it was new Dizzy caps.

    They were about 300 for 2 for the caps and rotor arms from the dealers so i'd check first.

    I had tracking on one of the points on the right bank.

    Dave!
     
  17. OP
    OP
    lynall

    lynall Hardcore MB Enthusiast

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    DPUL hope its not that as thats more than 50% of the value of the car!

    Uberwagon this engine has 8 seperate coil packs

    I have got to lift bonnet again as i woke up thinking i may have left a breather pipe off after removing the throttle body:eek: , so when its light enough i will check, cross my fingers i may have fixed it after all:)



    Lynall
     
  18. OP
    OP
    lynall

    lynall Hardcore MB Enthusiast

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    Nope i had refitted the hose:)

    Just been for a drive and in am sure the tickover is higher than before

    As i have cleaned out the throttle body with carb cleaner and removed all the gunge i am guessing it is now to far open?

    Does the engine relearn a new tickover speed or does it need resetting?

    Off to the coast later so i will see if it gets any better.




    Lynall
     
  19. Dieselman

    Dieselman Banned

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    It shouldn't change as it's controlled by the ECU. A quick check is to run the engine in neutural then engage drive, the idle speed should stay constant.
     
  20. OP
    OP
    lynall

    lynall Hardcore MB Enthusiast

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    Dieselman thats exactly what i noticed as i sent from drive to reverse to park in my drive that the revs surged up to about 1k ish then slowly settled.

    Done about 100 miles today and its totally back to normal, well the tickover anyway, seems smoother to drive but the slight misfire is still there:cool:



    Lynall
     

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