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Rough running engine (sticky exhaust valve, or blocked injector?)

I had once this symptom on an io360 it was an injector. I would start with the obvious.

EBST

Another thing to inspect is the exhaust muffler, I have known baffles in the muffler come adrift and restrict the gas flow from one cylinder.

Indeed, but this issue is most visible at low revs i.e. low gas flows, etc. At say 2000rpm the engine runs fine.

This issue is noticed only because I know the plane well and am diligent in preflight tests. Prob99, a renter would have just gone for a flight

I am ordering a replacement injector from GAMI. It is a particular aperture, of course. I thought I had a Lyco injector in stock but I can’t find any.

I had once this symptom on an io360 it was an injector. I would start with the obvious.

Was it also running (apparently) too rich?

Administrator
Shoreham EGKA, United Kingdom

A_and_C wrote:

Another thing to inspect is the exhaust muffler, I have known baffles in the muffler come adrift and restrict the gas flow from one cylinder

THis would be more noticeable at high power than at low power (which is the case here), would it not?

A blocked fuel injector would be noticeable at higher power too, but Peter shows no symptoms at 2000RPM or higher..
A blocked fuel injector air inlet has zero effect at large throttle openings (Peter’s typical climb and cruise modes) but would show at low power.

If anything, swapping injectors is easier than removing exhausts, not to mention exhaust valves…

Antonio
LESB, Spain

Peter wrote:

I am ordering a replacement injector from GAMI. It is a particular aperture, of course. I thought I had a Lyco injector in stock but I can’t find any.

YOu can just swap with any other cylinder and confirm if the fault moves with the injector, easy job.

Antonio
LESB, Spain

Hopefully it is just as easy as a new injector

Regardless, fuel injector ultrasound cleaning in a bath of mouse milk every 100-200hrs is a good preventative idea

Antonio
LESB, Spain

It would take quite a lot to bung this up…

People also soak them in MEK.

Oil analysis just came in – looks fine

Administrator
Shoreham EGKA, United Kingdom

did you note your fuel flow? normally at higher rpm, you’d see higher fuel flow than usual if the injector is clogged.
My vote is also on injector issues seeing that nr 2 pretty much gets cold with egt and cht dropping at the same time.

Switzerland

I get only the fuel flow for the whole engine, and the 1 cylinder being abnormal would not show up.

Administrator
Shoreham EGKA, United Kingdom

That’s not right. Any bit of blockage in any injector would cause pressure increase and false indication of unusually high fuel flow rate overall. If you know your normal fuel flow rates, it is an easy way to verify during run up.

Switzerland
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