T206H: Morning Sickness or Normal Warm-Up?

delta727

Filing Flight Plan
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Feb 23, 2018
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delta727
Hi Everyone,

Have been reading a lot about “morning sickness” and sticky valves on Lycoming engines. Curious where you draw the line between a normal warm-up and what might be considered abnormal for a TIO-540-AJ1A.

In short, I’ve noticed that right after a (hangared) cold start and at 1000 RPM, the engine sounds like it’s not quite “firing on all cylinders.” When I increase to 1200 RPM (to begin leaning for ground ops) the engine smooths out and there’s nothing else abnormal from there. My only other observation is that one cylinder is slower than the other 5 to register a “bar” on the EGT gauge but this always resolves during the run-up when I flip to a single mag and that cylinder is pretty close to the others in cruise.

I always had assumed this throaty, “chug-chug” sequence was completely normal for the engine as it warms up. But it also occurred to me that a sticky valve might also be the culprit before it “shakes loose” at 1200 RPM and is fine the rest of the flight. Is there any good way to tell the difference?

Thanks for any experience you can share.
 
You need to look at the engine monitor data. Cold EGTs can be a stuck valve or clogged injector.
Can you download the EM data and take a closer look?

Tom
 
What you are describing is classic valve sticking. Having your shop periodically cleaning the valve/guides is good preventative maintenance. See Lycoming Service Instruction 1425. The warnings you get are limited.
 
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Define cold start, how cold are talking here?
 
What oil are you using, and ambient temps?
edit: Oh, and how many hours/years is the engine.
@delta727
 
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I thought the first few seconds can be kind of rough while fuel hits all cylinders. And was told with morning sickness it would run rough for like 30ish seconds which is a long time and be considerably rough running.
 
Describe your priming. How does your priming differ as temps change? No preheat?
 
If you determine it's morning sickness keep an eye on it. You might get yourself a nice O-145 and you wouldn't want to not be there for the miracle of birth.

It hasn't been mentioned, but plugs are a part of the formula too and easy to check on. As the owner, you can pull them yourself and if you choose to do so, do it when you would normally fly. When you do, they should be ash grey in color, free of lead buildups, have no cracks and be properly gapped - you'll need a feeler gauge to check that. If they're black and icky, it's a sign that something is wrong, you're running too rich or you have another problem (like rings) which is putting excess oil or fuel into the cylinders.

Could be that you start up, run lean and run the crud out of the plugs so they start firing better.
 
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