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IO-360 Strange Start Problem

L'Avion

Well Known Member
IO-360, high comp pistons, starts normally, then fumbles, runs rough, and #2 EGT is abnormally low; condition doesn't smooth out. Engine shutdown, wait a couple minutes and restart; and restart cures the problem - no further problems. Plugs have been cleaned (look good) and the fuel line to #2 has been removed, blown out clean --- same problem persists. Mystifying!

Any ideas?

Barney, in Memphis
RV-4 flying
RV-3 flying
 
Potential induction leak. Something may be cracked and have a gap when it is cold, then the assembly heats up, grows due to the heat, and seals the gap.
 
Stuck Exhaust Valve = Culprit

Engine has 4 into 1 exhaust: We pulled the prop through while listening with our best ear at the exhaust pipe. Three cylinders exhausted with a BIG POOF, and the culprit just hissssssed!

Barney, in Memphis
RV-3 flying
RV-4 flying
 
Morning Sickness

The Dec 2010 online issue of Kitplanes has a very good article explaining the problem and how to fix it.

Title of article > Morning sickness: It?s about sticking valves.
 
Textbook symptoms of a stuck exhaust valve.

Since it's a high compression engine, I'd advise borescoping it to see if the exhaust valve isn't burned. The rope trick, or even "staking" the valve with the rocker cover removed may only temporarily postpone the inevitable need to pull the cylinder off and send it to a cylinder shop for a proper fix.
 
Problem Fixed - Back in the Air

The problem was a sticking exhaust valve on #2. Valve was dropped into the cylinder, dragged out a the lower spark plug hole, and the stem was cleaned. Valve guide was reamed, and everything was reassembled - ground run & flight test, A-OK. The other three exhaust valves will be checked and the guides reamed (if necessary-sticking at all) at the next oil change.

Link to some helpful valve poop:
Everything You Ever Wanted to Know About Lycoming Valve Failures
http://egaa.home.mindspring.com/valves.html
 
Sweet

Now just never use 100ll ever again and the problem shouldn't come back..:)

Frank
 
I just bought a RV 8-A 10 days ago and had to do the same thing. I changed from 15-50 Aeroshell to Phillips I run in my Cessna 180 with camguard. I'm hoping that will help.
 
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