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Thread: Engine Breaking Up At High Rpm

  1. #1
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    Dec 2004
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    Default Engine Breaking Up At High Rpm

    Looking for some help! My Noble at high RPM is breaking up. At one time it was 4,000 RPM range. Now that we gapped them closer from .040 to .038 it moved up the RPM band to about 5,000 RPM. We then installed new plugs and the problem is still there. We are thinking maybe a a weak coil. How about any other suggestions?

    Thanks!

  2. #2
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    If you are at a loss, you could try emailing Trevor via his profile on pistonheads :

    http://pistonheads.co.uk/members/sho...?memberId=1984

    He works for Roush UK and did all the mapping etc for the 3l engines so knows his stuff. Although I know you guys have a slightly different spec and perhaps map?


    sold : M12 GTO3

  3. #3

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    Check coil packs, unplug from loom and spark-plug and reseat.

    Check plugs - correct spec and grade?

    Check Fuel Delivery - may be difficult, how noisy is the pump? Loud buzz is pretty much normal but any rattle or occasional grinding noise is bad. Change the fuel filter as a precaution in case it has become blocked. Unlikely as a change in plug gap resulted in a change in syptoms

    If possible plug a laptop in with Easimap w/ 975 support and check what happens when the mis-fire occurs i.e. is there a sudden sensor dropout or strange reading?

    I'd suspect a failing coil pack or poor connection to one pack as primary candidates for the failiure point.

    Best Regards
    Matt

  4. #4
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    Thanks guys. I know KTR in Ayer Mass who did the install has tried to contact Mike for coils. Fuel pump seems good. Plugs are all new. Do the new coils come with the rubber boots? Does the coil have a wire in the boot? Seems like one assembly.

  5. #5
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    Please keep us posted on what you find. Mine is doing the same thing. Haven't had time to collect the data on Easimap yet. My wife has me going on a stupid cruise. Dean

  6. #6
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    According to KTR it was a vaccum leak on the throttle position sensor.

    Not sure, but the problem is gone.

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