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engine trouble shooting help please

Lan Vinh Do

Well Known Member
HI
Since a year I experiment rare event of 1 or 2 second only.
i normally have vibration for 1 to 2 second and it stop. When it happened in calm air, i had the feeling that i hit something with the wheel pant ( just the sound)
At begining, i tought i was crossing the turbulence of another aircraft as it often happen near a airport.
The majority of the time, it's after levelling or in a descent after a long flight. It happened once juste after take off ( 20 ft in the air ) but it was just after a run-up after without the cowling ( after the annual) put back the cowling and doing a test flight.
it was happening before this inspection. All spark plug has been change, mag was sent for the inspection and reinstall, fuel filter all clean, gascolator filter clean.

i have a io 540 new from aerosport with a silver hawk ex, one mag, one plasma III.
no water on the preflight check. Plane always inside when not flying.

today it happened just une minute after levelling, flew over the airport and mag check and llama III check ok.

I download the engine data and after zooming it, i can see the get of cylinder no 2 went down from 1164 to 1143 in one second and stayed there for 4 second before to go up again exactly at the moment of the vibration. I was was just touching the mixture to lean but i don't think i had the time to really lean.

4c49a703-2ee9-4b3f-a028-874840308fc9_zps6969172c.jpg


Mag check and plasma III check
magcheck2_zpse81adaf5.jpg


It happened another time in a descent fuel pump on in final. again only 1 second. always cylinder no 2 ( orange)
6514742f-12e2-4cea-9489-5293ee377e16_zpsc9473ee2.jpg


all other engine parameter normal. Fuel pressure, FF, oil temp, CHT. it's so short that it's hard to pick.

any idea?.
i don't think it's the ignition as the get go down and it mean that my mag and plans III would need to fail at the same time. ( because the get go down and not up) Am i right?

thank you
Lan Vinh Do
 
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Data sent

I sent the data to savvy yesterday. Will post the answee when available. I don't have any morning sickness. The only other problem is after a hot start, the engine sound like it want to quit at idle. But i think it's not related.
Any other clue is still welcome.
 
This sounds like exactly like what I had,, same issue at level off and decent, we found #3 cylinder was sticking.
 
No sticky valve.

I inspected the valve of no 2 cylinder yesterday with a mechanic. No sticky valve. Any other idea?
 
So this is happening shortly after a power reduction. I would check for a small induction leak that would cause a lean cut out condition. When the manifold pressure goes down, more air is sucked in thru the leak which causes that cylinder to go lean and misfire.
 
Normal report from savvy

I had the report from savvy this morning. Normal. For me it wasn't normal in the cockpit. I will email back to discuss because the egt really go down at the exact same time.

My engine is a 2006 aerosport with only 400hre.
I bought the ane in 2011 with only 100hre ( first flight in 2008) but sice 2011 the plane fly at worst each 2 week and normally once a week.

For the valve, we were begining the service instruction 1425a we took out the rocker and spring and was expexting to find a sticky valve but it was really smooth. O resistance at all.Video scope also cometely normal for cylinder and valve. The mechanic have stop there because he was sure it was 't the problem.

I will search for a induction leak or air suck somewhere in the fuel system. I may put new coils on the plasma III or change the box too.

I don't know. I hope i will find the problem.
 
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found it.

Thank You BOB.
you are my hero.

I overlook the intake of cylinder no 2. Why. Because i had a leak at last annual on cylinder no2. I bought the gasket and gave it to the mechanic that work on my airplane. he clean everything and reinstall. So new gasket 30hre ago... didn't took a close look.

Today, did a better inspection after the comment of BOB. To easy... NO INTAKE GASKET. the intake was reinstalled by the mechanic without the gasket.

So a maintenance induce failure.
It should solve the problem. I will put everything back together and should to a flight test this week end.

Thank you everybody for your help. At least i learned a lot from my reading on this troubleshooting. Just a little bit disappointed that i received a normal report from Savvy sending my engine data and telling exactly when happened the problem with the EGT going down.
 
mech

Give the mechanic that assembled it a ton of s***! He/she deserves it.
 
Thank You BOB.
you are my hero.

Thank you everybody for your help. At least i learned a lot from my reading on this troubleshooting. Just a little bit disappointed that i received a normal report from Savvy sending my engine data and telling exactly when happened the problem with the EGT going down.

I don't find much value in oil analysis or EGT/CHT log analysis other than to get you which cylinder is acting up.

I've seen oil analysis that came back great while the filter was full of shavings...same sort of deal.
 
Bob

Is it not the case to use all the information available to help monitor the health of an engine?
 
If a metal particle is not large enough to be caught by the filter and visible to the naked eye its not worth worrying about.
 
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