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Hello!

I have an F model with the A1A. I’ve been having this issue on the ground shortly after startup. I have a JPI 900 and can see my EGTs rising fine initially, however sometimes the second cylinder dies. If I pull power back to about 800 RPM it tends to eventually run fine. The cylinder goes from around 1300-1400 EGT at startup (around 50 difference) down to 600. I’m usually at around 1,000 RPM when it happens. It shakes pretty severely. In addition to on the ground, I can’t lean to peak in flight (I run ROP). It will stumble similarly on the ground. 
 

We’ve swapped plugs with other cylinders, swapped injectors, compression tested (80/80), overhauled fuel spider, blown fuel line from spider out. 
 

Just looking for advice if anyone else has had this problem. I do have a video of the engine monitor when it does this if that helps. 

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Since it’s isolated to one cylinder it’s either fuel air or ignition related, you have already ruled out the obvious with spark plug,injector swap. I’m inclined to think it’s air related. I would inspect that cylinders induction tube and change the gasket.

it reminds me of an intake leak/ cracked cylinder 

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There could be more than one issue manifesting as a single symptom.  Would be a good idea to verify that idle mixture is within specs. I would check for a rise in RPM when going to idle cut off ( I do it both 1000 RPM and idle rpm). Start up EGT‘s of 1350 to 1400 suggest a relatively lean mixture at first full rich. My engine idles a bit richer than that if I recall correctly.  I would have to manually lean my A1A too see EGTs that high. 

The reason I mention multiple issues is because I would not expect a cylinder to drop off from a typical intake leak unless the mixture was all ready fairly lean. 

All of the above being said, im leaning towards an ignition issue given the symptoms in flight. Several years ago my partner called me after scrubbing a trip due to in flight symptoms almost exactly like the one you describe.  The difference is that the ground ops and run up (Standard 1750 RPM full rich, mag check) were fine. When I investigated, I found that one of the plugs on the offending cylinder stopped firing at about 2100 RPM (distinct EGT rise starting at that rpm without touching the mixture). He was essentially trying to lean an engine that I had duel ignition points on three cylinders and a single ignition point on one.  The ending would start to run rough long before reaching Peaky GT due to the protracted combustion event from the slower flamfront on the offending cylinder. In our case it was a defective champion plug.  Could be an ignition lead in your case.

 

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Make sure your sniffle valve is operating correctly so as to drain effectively after shut down.  A while back, mine was stuck closed and caused fuel to pool up in the intake plenum.   The symptom was very similar to morning sickness / sticky valve on the ground.    There was a glob of something in it I assumed to be a bug that came in through the ram air door.    It takes 5 minutes to remove and soak in 100LL or hopps.  

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2 hours ago, Browncbr1 said:

Make sure your sniffle valve is operating correctly so as to drain effectively after shut down.  A while back, mine was stuck closed and caused fuel to pool up in the intake plenum.   The symptom was very similar to morning sickness / sticky valve on the ground.    There was a glob of something in it I assumed to be a bug that came in through the ram air door.    It takes 5 minutes to remove and soak in 100LL or hopps.  

I don’t think that would cause the issues he’s having in cruise.

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31 minutes ago, Shadrach said:

I don’t think that would cause the issues he’s having in cruise.

You’re probably right, but takes only a moment to rule out for no cost.   

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4 minutes ago, M20Doc said:

I vote sticking valve, it will pass the wobbles test if the guide is full of crap.  Do the rope trick and ream the guide.

Clarence

 

Seems odd that that would cause his cruise issue of not being able to lean to peak before roughness,

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Shaking, rough running and cold EGT then running smoothly sure sounds like a sticking valve.  It takes an hour to check and ream a cylinder.  In the mean time the sticking valve causes the lifter face to scuff and take out the camshaft.

Clarence 

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On 6/24/2022 at 12:25 AM, Colbyw said:

Hello!

I have an F model with the A1A. I’ve been having this issue on the ground shortly after startup. I have a JPI 900 and can see my EGTs rising fine initially, however sometimes the second cylinder dies. If I pull power back to about 800 RPM it tends to eventually run fine. The cylinder goes from around 1300-1400 EGT at startup (around 50 difference) down to 600. I’m usually at around 1,000 RPM when it happens. It shakes pretty severely. In addition to on the ground, I can’t lean to peak in flight (I run ROP). It will stumble similarly on the ground. 
 

We’ve swapped plugs with other cylinders, swapped injectors, compression tested (80/80), overhauled fuel spider, blown fuel line from spider out. 
 

Just looking for advice if anyone else has had this problem. I do have a video of the engine monitor when it does this if that helps. 


This would be a great discussion for…

https://mooneyspace.com/forum/43-engine-monitor-discussion/

Why are we not using the engine monitor data?

usual steps for somebody with a powerful engine monitor…

1) download the data…

2) send data to Savvy…

3) Click the share button at Savvy…

4) Post link here

5) Sticky valves often show their fingerprints in the graphs…

6) Stuck valves often leave a foot print on the piston crown…

7) Foot prints on the piston crown can lead to bent valves…

8) Bent valves can lead to really long days and expensive fixes…

9) Use the monitor’s inherent skills and get your money’s worth!

Or did you get the monitor with no memory to be downloaded?

This came up the other day…

:)

-a-

 

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