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lumpy tick-over

Discussion in '456/550/575' started by AndyE, Feb 18, 2007.

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  1. AndyE

    AndyE Karting

    Jul 5, 2004
    161
    Gloucestershire
    #1 AndyE, Feb 18, 2007
    Car seems to perform OK, and there is no missfire once moving. But once the car settles down to idle - the tickover becomes lumpy and the revs aren't completely steady, if I hold the throttle at say 1500 rpm it it smooth or seems so anyway.

    I'll mention it when I get it serviced in October - so they can find something wrong and get lots of money out of me. It doesn't really bother me that much, I am just worried that it is a symptom of something else.

    Any ideas anyone ??

    Cheers
    Andy
     
  2. t024484

    t024484 Karting

    Nov 9, 2006
    171
    Netherlands
    Full Name:
    Hans A. Polak
    #2 t024484, Feb 18, 2007
    Andy, what is the car that you are having problems with, is it the blue 456 M GT in your profile ?
     
  3. AndyE

    AndyE Karting

    Jul 5, 2004
    161
    Gloucestershire
    #3 AndyE, Feb 18, 2007
    Yes, same as profile.
     
  4. 575M-Nero

    575M-Nero Formula Junior

    Feb 25, 2006
    524
    #4 575M-Nero, Feb 18, 2007
    Broken valve spring?
    Bad spark plug/wire?

    Don't rev it high until you diagnose.
     
  5. AndyE

    AndyE Karting

    Jul 5, 2004
    161
    Gloucestershire
    #5 AndyE, Feb 18, 2007
    Ooops, I've kicked the crap out of it since day one :)

    (I will get it checked out soon though).
     
  6. mont

    mont Formula 3

    Sep 16, 2004
    1,551
    Portugal
    #6 mont, Feb 18, 2007

    Hi Andy,

    Take out the spark plugs and see how they look, I bet you have one oil fouled.
    If so, bad news, I think you have a valve guide problem. If they are okay with the greyish color and dry. Start to look to a bad connection somewhere. Cables, relays, power ecu for each bank, etc...

    Mont
     
  7. vandevanterSH

    vandevanterSH F1 Rookie
    Silver Subscribed

    Jan 27, 2005
    3,144
    AR
    Full Name:
    Stephen Van Devanter
    #7 vandevanterSH, Feb 18, 2007
    I had a similar problem with 575; turned out to be a leaking intake gasket. This type of problem is discussed by rifledriver in the 456 valve guide thread.

    Steve
     
  8. AndyE

    AndyE Karting

    Jul 5, 2004
    161
    Gloucestershire
    #8 AndyE, Feb 18, 2007
    Thanks for the replies so far. I had a full service in Oct and I have all the spark plugs that were previously in. I seem to remember they all looked OK. I'll double check tomorrow. What are the other symptoms of valve guide problems? Smoke?
     
  9. mont

    mont Formula 3

    Sep 16, 2004
    1,551
    Portugal
    #9 mont, Feb 18, 2007
    Smoke is "tricky".
    If the problem just showed up the smoke is almost non present, i.e., just some when you start engine and then no more.
    Only if the problem was severe there was some visible smoke.
    You should look to the new spark plugs.

    Also, check the oil level and the water temp. gauge. while driving. With a valve guide problem water temp. is a bit higher.
    But, most important is to diagnose the right problem so don't loose your sleep yet.

    Mont
     
  10. 575M-Nero

    575M-Nero Formula Junior

    Feb 25, 2006
    524
    #10 575M-Nero, Feb 19, 2007
    Mmm, ignore the valve spring comment.
    Maybe a spark plug wire is burnt?
     

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