popping/backfiring noise

[greg51]

I am noticing when I pull the power back to land a slight popping noise. I am thinking a small exhaust leek, any comment?

65 m20E

[Mikey30V]

My mechanic said last year that if the induction tube gaskets at the cylinders are leaking, the high vacuum at low power settings will make one or more cylinders run lean and pop.  Last year he changed my induction gaskets (but not the induction hoses, and not the exhaust gaskets) and my popping problem on short final and in the flare went away.   Might be worth a look at the induction gaskets if they are over 5 years old. 

[powder_hounder]

I've had this occur in the past, right after my mags were 500 houred. When the mags were reinstalled they were a tad too far advanced timing and was causing weird pops and backfires such as this on final and taxi.  When this was occurring, the left mag barely showed 10 RPM drop during run up, but the right mag was showing 80-100 RPM drop. I retimed it in my hangar with my IA and we retimed using his nosecone angle thingy, and mags both showed approx 50 RPM drop and we were good. Pops and backfires went away. 

[1964-M20E]

Check induction system for leaks.  I just had a major induction leak on #3 the bolts holding the induction tube came loose and fell out.  When I reduced power the engine began running rough #3 not firing well or at all.  Taxing to the FBO several pops and rough running.

 

[greg51]

Thanks to all, I just spoke with my mechanic and he agreed. I just had a new cylinder #3 put in and a couple of heat cycles could have loosened the induction tube.

[Guitarmaster]

I retimed it in my hangar with my IA and we retimed using his nosecone angle thingy,

Is that in the Lycoming parts list?

[powder_hounder]

If it's not, it should be.