Lycoming YIO-360-M1B (180HP) question

Folks,

I am Brazillian so make an allowance and forgive my english writing.

Recently a friend of mine bought an used RV7A with a LYCOMMING YIO-360-M1B (180HP). This plane had a history of incident with main gear failure and flip.

It was repaired with the insurance company money from a reputed company that made all tests to the engine and complete rebuilt the airframe.

After the purchase... We've flown couple hours on the plane without problem on take off or cruise except a great difficulty in maintaining it at idle or bellow 1200 rpm for warm up when starting cold.

But even after a flight (with the engine already warm) when I quick stop in pump for refueling after re-starting it was again dying on idle with much gasping and choking. And it seems to be getting worse...

We notice also some loise "shots" from the exhaust sometime on take off or when we idle it on final.

It got worse, last flight had to be aborted because the engine had vibration on high RPM , noise a bit out of common and was noticeably producing less power that I was used to have...

I TALKED to a mechanic that had not time yet to verify it , but he will.

Before that I would like any opinions on what could be the cause for an engine that was behaving ok on one week had such fast degrading simptoms.

- Magnetos tests where a bit high but about normal , 200 rpm drop and same on both magnetos...

- Propeller pitch test producing drop as expected and re-establilish values after..

But the engine continues to behave badly on idle or low rpm (dying) and also in take off power (vibration , shots from exhaust an seems to produce much less power than expected)
I thought:

- Spark plug oil-fouled - if so why I was not able to dry it on low mixture (tryed for 2 min!)?

- Contant Speed governor was unable to bring the propeller pitch to the correct take off position (less probable to be the cause)

- Others....( injection settings? )

Obs: Engine is in break in period after having being inspected and rebuilt.

Could anyone point other probable causes of the power loss, exhaust shots and dying at low RPMs?

Thanks in advance.

My experience breaking in my IO-360-M1B was as follows:

During break in, I had to lean on the ground aggressively to keep the engine from fouling the plugs. (Home airport is 2200 feet elevation). Leaning during runup would clear it though.

Additionally, I chose to look at the plugs frequently (about every 10 hrs) and swap them top to bottom in order to keep them clean.

As the engine broke in, the need to lean aggressively while taxiing was reduced but in order to get a good mag drop, leaning is still required. If I don't, I get the 200 rpm drop you mention.

Thanks Bill I do agree with you !

Up to now, before a closer look scheduled from my MECHANIC yet to be done, I think the roughness on idle and take off , the backfires (scattering missfire), the power loss must have three causes (aggravating one another):

- fouled spark plugs
aggravated
a- very rich mixture (injection settings must be verified)
b- break in period (piston ring is still setting and does not scrubs oil as it should fouling spark plug is easier so...)
c- bad magnetos settings (Defective magneto breaker points / Dirty or broken carbon brushes in magneto)

I think it is a combination of a, b and c making it very difficult to clear through a simple leaning...

Lets wait the mechanic tests...

Thanks!

It sounds to me like you have a bad air leak on one Intake pipe. This will always cause a rough idle, sometimes popping in the induction system from being lean at low power and idle. Replace leaking intake gaskets.
You should also check and clean all injection nozzles it sounds like you have one that is partially obstructed.

Thanks Booby I'll have those checked also...

It was a very very dirty injection nozzles. Strange is that there were filters on the fuel line and they were clean...

The mechanic cleaned the nozzles and the engine performed as usual, but I still don't know what made so much dirt to block them.

The debris where composed by something looking like black rubber fragments , from a hose maybe...