Question Momentary engine shudder and CHT temp alarm

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26 Mar 2022 18:52 #3438 by STEVE ELLS
Replied by STEVE ELLS on topic Momentary engine shudder and CHT temp alarm
Hi John;
I'm glad your engine is running well.
I asked for pictures because it's very unusual for spark plugs to actually be broken. Glad my advice on the 5K ohm check was helpful.
Steve

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25 Mar 2022 11:56 #3437 by John Clark
Replied by John Clark on topic Momentary engine shudder and CHT temp alarm
Hi Steve,
My A&P is the one that found them. He didn't take a picture. He just said the lowers were broken. After I told him about the 5K ohm check you mentioned he went back and checked the rest and found the other three bad ones. Sounds like I was lucky that is all the problem I was having.

I took the plane around the pattern a couple of days ago on a warmer day and all CHT and EGT temps were much lower. Lowest I remember seeing them in the year I have had the plane. Definite improvement in performance.

Thanks again for the assist.

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21 Mar 2022 14:53 #3436 by STEVE ELLS
Replied by STEVE ELLS on topic Momentary engine shudder and CHT temp alarm
Hi John;
Wow! That's surprising.
Please post a picture of the plugs that were broken?? I'm very interested in which part(s) were broken.
Thanks for the feedback.
Steve

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17 Mar 2022 18:29 #3435 by John Clark
Replied by John Clark on topic Momentary engine shudder and CHT temp alarm
Hi Steve,

Found a total of 5 bad plugs. 2 were physically broken including cylinder 2. 2 failed spark test and one had high resistance. Also found a broken intake gasket on cylinder 2 which was replaced. Going to take it out tomorrow for a long check ride, but I am fairly confident she will be purring again. Thanks again for the advice.

John

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13 Mar 2022 09:40 #3429 by STEVE ELLS
Replied by STEVE ELLS on topic Momentary engine shudder and CHT temp alarm
John,
I suggest you check the electrical resistance between the spark plug spring contact inside the barrel of the plug and the center electrode at the firing end.

Any resistance over 5 K ohms will cause problems. Replace any plug with resistance over 5K ohms.
Best,
Steve

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12 Mar 2022 19:45 #3428 by John Clark
Replied by John Clark on topic Momentary engine shudder and CHT temp alarm
Hi Steve,
Thank you for the quick reply. The engine does not suffer from “morning sicknesss”. Just had an annual in October with new plugs. I know that doesn’t mean anything since new plugs can be bad, wrong gap, etc. also, didn’t have this problem before the annual. Will definitely try the swap.

I saw the rope trick in service instruction 1425A. Since he checked the cylinders iaw SB 388C I don’t think he saw the need. If the plug change doesn’t work, will try that for sure.

Thanks again. Should get the plane back Monday and will let you know.

John

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