Lumpy idle slight missfire…...help



  • hey guys/gals

    right this is what i've reacently done…

    6 x brand new NGK-R plugs
    6 x brand new HT Splitfire leads

    when i fist start the car it idle's fine, after i've been for a drive and hit a red light or compulsory STOP it idles really lumpy for some reason. also if i rev and hold the rev at a constant RPM i can hear it missing now and then(quite frequently actually).

    also i have checked the gap on the plugs...but dont really know what i'm looking for....however they all looked the same to me,(with regards to the bottom of the plugs and how far the spark has to travel and all that garbage....

    any ideas



  • lumpy idle can be a lot of things, maybe moved the cable on a sensor can do it sometimes, did you disturb the air filter + box because the first thing to check on an mx3 is if the induction pipe is leaking and lumpy idle and loss of power is usual result, you may have just leaned on it enough to crack it

    Because it is fine when its cold it will probably be the induction pipe from the throttle body to the air filter case, the engine is fine with lots of cold air getting in at the start but when it gets up to temperature and the mixtures level out, it doesnt want it anymore thus leaving it lumpy.

    Mine was the same when it went, did not even know what was happening but as the crack got bigger it got worse until the moment it snapped and then it stopped running altogether.

    If that is fine and it was fine before you fitted the plugs + leads get it hot so it starts running rough again and just remove 1 lead at a time
    BE CAREFUL NOT TO GET AN ELECTRIC SHOCK
    from the engine head - NOT THE DIZZY and when it just runs the same with the lead disconnected that will be the troubled one then its likely to be either a dodgy lead or plug

    Also if you have changed the leads check the distributor cap for any damage and inside is a rotor arm that may need changing too



  • more than likely its the pipe.

    but check the plugs as you may have to adjust them. youll need feeler gauges.



  • oh and maybe one or to leads might not be seated properly



  • @64b75e5dd6=tinyrhino:

    oh and maybe one or to leads might not be seated properly

    now you mention that, the leads click onto the plugs fine but the rear 3 seem kinda long about 1cm actually, the rubber gromits dont sit flush with rear rocker cover. but there the right leads for the car apparently…..


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