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Have an interesting problem I've been wrestling with.  EGTs are good at RPM.  When I throttle back as in downwind #1 EGT drops out the bottem.  I get an EGT out of range on the EFIS.  Add power EGT comes back up.

When I pull the plugs and inspect #s 3 & 4 are white.  #1 is black (as in fuel fouled) and #2 is black but not as bad as #1. 

CHTs on #1 & #3 are also a bit low in relation to #2 & #4

The only common item I can see to #1 & #2 is the trigger coils.  I have already replaced the IGN coil for #1/2 Bottem and all plugwires and boots that tested out of range with no real change.

Also both carbs have been to Lockwood for 600hr overhaul.

Any thoughts? 

  • Re: EGT issue

    by » 7 months ago


    The plugs are normal if the engine was idleing before shutdown. How many hours on the EGT's they have a life 300 to 500 hours some go longer. Replace all as a set otherwise you get mismatches on the readings.


  • Re: EGT issue

    by » 7 months ago


    Replaced the EGT less than 25 hrs ago because of the same problem before I replaced the IGN coil & wires.  ACFT has about 130hrs.  Eng has about 1300 hrs w/ a ZipperKit installed about 80 hrs ago.

    Shut down was right after landing and then the plug check.


  • Re: EGT issue

    by » 7 months ago


    Don't let it idle at all, after a ground run of 5000rpm shut it down immediately then check plugs. Have you weighed the floats and checked carburetor balance?


  • Re: EGT issue

    by » 7 months ago


    Float weight checked at condition insp. - Good and I assume Lockwood checked them when I sent them in for overhaul. 

    Also reset the carb balance.


  • Re: EGT issue

    by » 7 months ago


    Does make full power? Is the mag check during runup within specs? Was the coil bad that you replaced? Did you swap the EGT probes  and make sure it is not a problem with your instrumentation?


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