Low Temps on One Cylinder

Palmpilot

Palmpilot

Touchdown! Greaser!
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Richard Palm
If CHT and EGT is significantly lower on one cylinder than the others, and there is a slight roughness, is that an indication of plug fouling?
 
For me it was a sticky exhaust valve.But mine ran extremely rough.
 
FPK1 said:
What engine?
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The plane is a rental, so I don't know, but it's probably whatever is standard for a Citabria 7ECA. According to a copy of a Pilot's Operating Manual that I have, it would be an O-235-C1.
 
Palmpilot said:
The plane is a rental, so I don't know, but it's probably whatever is standard for a Citabria 7ECA. According to a copy of a Pilot's Operating Manual that I have, it would be an O-235-C1.
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Looks like a common problem with that engine... Google

o-235-c1 running rough

And you will find many possibilities...
 
FPK1 said:
Looks like a common problem with that engine... Google

o-235-c1 running rough

And you will find many possibilities...
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It's in the shop now, so I'll probably be able to see online tomorrow how it is resolved.
 
Palmpilot said:
The plane is a rental, so I don't know, but it's probably whatever is standard for a Citabria 7ECA. According to a copy of a Pilot's Operating Manual that I have, it would be an O-235-C1.
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I assume the plane has an engine monitor (since you know only one cylinder is cold). Any chance anyone (savvyaviation) can read that data? They have pointed out exhaust valve issues to me before.

What is your leaning procedure? It is usually lean till rough then richen till it smooths. Is that how you do it and it is still rough?
 
JOhnH said:
I assume the plane has an engine monitor (since you know only one cylinder is cold). Any chance anyone (savvyaviation) can read that data? They have pointed out exhaust valve issues to me before.
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It has a JPI EDM 930. I would be surprised if our mx department didn't have the capability to download the data. In any case, I don't have any doubt that they will be able to get to the bottom of it, so this is just a matter of curiosity for me.
JOhnH said:
What is your leaning procedure? It is usually lean till rough then richen till it smooths. Is that how you do it and it is still rough?
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The entire flight was in the pattern, so the only leaning was during taxi.
 
FPK1 said:
Did you do a run-up? Was it normal or rough running during the run-up?
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The roughness was barely noticeable at that time, and there was no increase in roughness when switching to either mag by itself. The amount of RPM drop and the difference between mags were within specs.

The plane was put back online half an hour ago, but the resolution of the squawk has not been posted on the Web site yet.
 
Palmpilot said:
The roughness was barely noticeable at that time, and there was no increase in roughness when switching to either mag by itself. The amount of RPM drop and the difference between mags were within specs.

The plane was put back online half an hour ago, but the resolution of the squawk has not been posted on the Web site yet.
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I suspect it will say "operator error".
 
Palmpilot said:
If CHT and EGT is significantly lower on one cylinder than the others, and there is a slight roughness, is that an indication of plug fouling?
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If one plug is not firing, CHT will be slightly lower, EGT higher as the combustion process will be late, allowing less time for gas to expand/cool. Sounds like valve issue. IIRC that engine requires periodic valve adjustment, no hydraulic tappets. Needs an adjustment.
 
PaulMillner said:
If one plug is not firing, CHT will be slightly lower, EGT higher as the combustion process will be late, allowing less time for gas to expand/cool. Sounds like valve issue. IIRC that engine requires periodic valve adjustment, no hydraulic tappets. Needs an adjustment.
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Sounds right especially in light of what was said in post # 12, "there was no increase in roughness when switching to either mag by itself" ...
 
PaulMillner said:
If one plug is not firing, CHT will be slightly lower, EGT higher as the combustion process will be late, allowing less time for gas to expand/cool. Sounds like valve issue. IIRC that engine requires periodic valve adjustment, no hydraulic tappets. Needs an adjustment.
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You're right. I have the identical engine out of the same aircraft in my experimental. Lycoming recommends checking valve lash every 100 hours.

Every condition inspection for 7 years I have checked this. None have ever needed adjustment. Certainly worth checking though.
 
The squawk has now been closed, with the following note:

"Inspected and cleaned spark plugs. Conducted run up, ops check ok."​
 
Jeff767 said:
The problem will be back.
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So far, strong crosswinds have discouraged anyone from flying the plane since I did, but I'm watching to see if any new squawks show up.
 
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