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Mis-fire in High gear

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  • [All Models] Mis-fire in High gear

    Hi, I have a 12 plate 1.2. over the last couple of days i have notced a slight mis-fire when in a high gear, maybe 4th or 5th and at low revs, maybe <3000 rpm. No warning lights ad seems fine other than this?

    Any ideas before i take it to the local garage?


  • #2
    When was it last serviced? A new set of plugs is always worth doing.

    Also - has this started after you bought fuel? Contaminated fuel can cause a misfire.

    Check also for damp in the electrics.
    1972 Viva restoration thread -


    • #3
      Hi, thanks for the reply.

      Due its annual service in July.

      Are the plugs fairly simple to change? any advice on which make to buy?

      It has been very wet in my area recently so could be the electrics, is there a simple way to check and dry these?

      Thanks again,


      • #4
        Annual service doesn't mean they changed or even checked the plugs. Some places just go on 50k schedule for changes and leave them alone. Halfords usually stock the Bosch plugs for those and they're decent enough. You can buy multi-tip plugs, they don't run any better they just last longer between services because as the gap to one tip gets too big another tip takes over.

        Re. the electrics - give the connections on the loom and the coil pack a good spray with WD40.

        To replace the plugs you need to remove the coil pack, treat it with care as rough handling or dropping can cause damage. Check the tips of the connections with the plugs for signs of discolouration or cracking - that's where moisture gets in and the current arcs to the head so you lose spark. You'll need a plug socket on an extension. Blast the plug recess with air before removing the plug to remove grit that will otherwise drop into the cylinders. Be careful refitting the plugs, don't cross thread them or over-tighten. The head is soft alloy. If in doubt use a torque wrench to make sure you don't strip the threads.
        1972 Viva restoration thread -