Io360 a1a cylinder blow by. Replace?

[Shadrach]

5 hours ago, LBM said:

What I think OP said was that he got an excessive drop on right mag, because it was contaminated, or mildly fouled, because of overly rich mixture during ground operations, and that he had to aggressively lean during runup to burn it clean.  You’re assuming timing is the only reason for anomalous mag drop, and it’s not.  It’s happened to me from overly long overly rich ground runs, and a very lean runup cured it.  What does that have to do with timing?

“Learning it out” will increase combustion temps thereby heating up the plugs to a temperature that enables lead bromide to convert to gas. I’m not sure what that does for an oil fouled plug.

Describing an engine that is only running on three cylinders as a 2-300rpm mag drop is a confusing way to explain what is actually happening.

[Teddyhherrera]

38 minutes ago, skykrawler said:

Pooled oil seems quite common with Lycoming's. My theory is it accumulates on the taxi back to the hanger.  I had a high time engine that did it - but when I landed from a 2 hour cruise and stopped the engine after a brief taxi, the lower plug was clean and a nice color.

My advice for getting a plug miss-fire from pooled oil during run up is to change the order of your checklist.

Move the mag check to the latest item.  Set the idle to 1200 rpm while performing the checklist.  And, do the propeller cycle check before the mag check.   Lastly, use the Lycoming documented procedure to perform the magneto check at less than full rich.

Its worth understanding that detecting plug miss firing is only part of what the mag check is about.  The normal 'drop' is a function of only running on one magneto.  The spread between the two can be a shift in the timing of the magneto or in the worst case some other real problem with the magneto (leaking coil- whatever).

I operate at an airport where on rare occasion there is the dreaded two mile taxi.  A good reason to lean as much as possible.

This is definitely what I think happened. After modifying my leaning, the problem has gone away

[A64Pilot]

On 11/1/2024 at 6:57 AM, Shadrach said:

“Learning it out” will increase combustion temps thereby heating up the plugs to a temperature that enables lead bromide to convert to gas. I’m not sure what that does for an oil fouled plug.

Describing an engine that is only running on three cylinders as a 2-300rpm mag drop is a confusing way to explain what is actually happening.

“Leaning it out” may burn carbon and fuel residue off of plugs making it so they will fire more easily, oil and or gas will allow a path to ground for the spark energy is why a “fouled” plug will not fire reliably, that and of course the compression in the cylinder also inhibits the spark, why sometimes a plug will seem to operate normally until it’s installed in the cylinder.

Decent video, Auto based and of course they are trying to sell plugs and at what Auto plugs cost, why not toss them?

Fuel fouling is one reason why a flooded engine is tough to start too.

Anyone who used to race two strokes is very familiar with plug fouling. Trail riding I would sometimes have to stop, pull the plug soak it in gas and just burn it to get it so it would fire reliably, this didn’t always work but often did.

A plug at higher power is a sort of glow plug in that it’s the hot spot in the cylinder, it’s that way to keep clean, obviously it’s a fine line getting it hot enough to stay clean, yet not so hot that it becomes a point of ignition prior to the spark

Edited November 2, 2024 by A64Pilot

[hammdo]

This should work ;o)

-Don