Lycoming 0360-A4A - 1500 RPM Hesitation

I fly a Piper Archer II with a 0360, normally aspirated. It has a slight hesitation when passing though the 1300 to 1500 RPM range. Just a hesitation, never anything more. Having talked to several A&Ps and having it thoroughly checked out, the consensus is, it due to a cut over from lower RPM carb jets to higher RPM carb jets and is common and not a concern. I have also noticed it is much more noticeable on hot summers days, and not noticeable in cold weather flying.

Has anyone else encountered this on an O360 or an Archer II? Any conclusions or remedies?

Harry Fenton is our Fly Baby engine guru, but he answers questions regarding other types of engines, too: harry@bowersflybaby.com

He discusses similar hesitation on an A65 at:

http://www.bowersflybaby.com/tech/fe...a65_hesitation

Ron Wanttaja

A couple of things to check would be the accelerator pump linkage and condition of the pump plunger or the idle mixture being too lean. Internet diagnosis is difficult at best.

It sounds rich. When an engine is cold it takes more fuel to keep it running correctly. Once it warms up if this mixture does not lean you will get a rich condition. Until the butterfly opens enough to bring in enough fresh air she stumbles.

This could be an accelerator pump set a little rich. Ones she warms she gets just a bit to much squirt of fuel and it takes a second to clear. When cold its not as noticable.

My thoughts on this.

Thanks for for the insight and advice. I think my next step is to seek out a carb guru in my local area. It is clearly an improper air/fuel mixture that happens at a specific RPM.

I have a 1979 Archer with the O360A4M engine and it has a hesitation when passing through around 1600 RPM. Its been that way since since I bought the plane in 1988. I am getting a reman engine in the next couple of weeks and I will let you know if it is still happening.

Mike

I have seen that type hesitation twice on my carbureted RV-6. Both times, the carb was slightly loose and throttle position was causing a vaccum leak. The solution was to remove the carb, replace the carb/sump gasket, and retighten and safety the bolts attaching the carb.