Flyman2456

Update: Checked sniffle valve, timing, and adjusted idle mixture. Sniffle valve was not it. Mag timing was reset and idle mixture was adjusted. Mechanic checked for leaks and increased the idle mixture fuel flow and after some fine tuning, it did not stumble or pop on the ground after my last 1.5 hour flight. Going to take it up once more to confirm it doesnt have the issue on the ground..will post an update and confirm if that fixed it. Thanks!

Exactly what I was thinking. I think at this point I'm just going to replace all gaskets and seals.

Is this the right angle fitting on the bottom of the sump? It has a hose connected going out the bottom of the cowling. This would be an easy test that I could perform but doesn't necessarily answer the question about why it only stumbles when the engine is hot..

Update: Cleaned and inspected all spark plugs. Two of the champion plugs that had greater than 5k resistance where replaced with new tempest plugs. An induction leak test with soap and water was performed around all intake seals and gaskets with no leak indications. Taxied out and did a runup and everything was perfect, RPM was stable, no stumbling. Then after taxiing a little more it started again, stumbling and popping. My next step is going to be to just replace all gaskets and seals on the intake. I'm thinking maybe when the engine heats up a small leak is introduced in the intake. Will keep posting updates. Thanks. Evan

@Hector That's what we were thinking about as a possibilty too

Also curious, is it normal to have different GAMI spreads at different Manifold pressures (i.e. I had a spread of 0.1GPH at WOT, and 0.4GPH at 17MP)??

Okay, I'll have to check that out as well...thanks! I'll still post the times for the data when I get a free hour or so.

I'm thinking right now I will first inspect and clean the plugs. If that doesn't fix it, move to injectors/intake, and mags/timing.

I'll have to go through tomorrow and add the times at which each test was performed. Just thought I'd post it now and see if anything popped out.. Thanks. @Hank The temps were upper 80's to low 90's. In Florida where field elevation is approx. sea level.

At 00:10:00 the left mag is checked then back to both at 00:11:00, then right mag at 00:12:00. No roughness with either on the ground. In the air the Right mag exhibited some roughness.. Hmm at 00:10:00 it looks like the EGT's seem to follow the same trend to me..

I went for a flight this evening and performed several mag checks and gami tests. 1) Ground taxi and run-up https://www.savvyanalysis.com/flight/3465025/a8524161-baaf-4704-9792-3a6adbb677bd 2) Flight https://www.savvyanalysis.com/flight/3465026/8f5f10b1-19ed-4673-90b5-8f7fe8b72f82 3) After landing and taxi https://www.savvyanalysis.com/flight/3465028/9114a858-1249-4562-b545-c388a3fb3974 A few notes: 1)- Ground taxi and run-up: Leaned for taxi, no stumbling noted. -Run-up, minor stumbling, increased mixture to full rich, raised RPM to 1700, performed a mag check. Some popping/stumbling noted. 2) -Take-off: no stumbling noted. -Cruise: Performed a GAMI spread with Wide open throttle (WOT), 2450RPM, with a result of 0.1 GPH spread. Then performed a mag check at 30-50 LOP. Noted right Mag was rougher than left mag. Performed a GAMI spread with WOT-10 inches MP (~17MP) and got a GAMI spread of .4 GPH Descent- Brought throttle to idle, no stumbling noted. 3) -After landing, leaned for taxi, lots of stumbling and popping at 1000 RPM, brought throttle lower and no stumbling noted. Brought to 1000 RPM and mixture slowly reduced and engine shut down. There was no increase in RPM when pulling mixture. I can elaborate on any of the above if need be. Let me know if anything stands out. Thanks in advance!

The spark plugs are the Tempest UREM38E plugs. The hours depend on which plug, some were replaced, would have to dig through the logs. Plan is to run it again this evening to gather more data and upload tonight. Thanks!

Do you recommend going full rich for the run up? Also how would you determine what cylinder has an intake leak?

Thanks @carusoam. I'll do another ground run with mag checks and before I shut down, go full rich, slowly lean until it shuts off and see what kind of rpm increase I get. I will post the data, thanks!

Thanks for the suggestions on mixture settings but just to note, I have tried it in multiple positions and the mixture setting seems to have no effect on the stumbling.

@carusoam Thank you for your input. Correct, the saw tooth observed was only during the ground runup. I did not experience any stumbling or popping during flight. I can spend more time during the ground run collecting data and doing the mag checks if that would be helpful. I will upload my results. Thanks! @Ragsf15e I have been leaning very aggressively during taxi. Like you said, just slightly rich of the point it runs rough.

The sawtooth was interesting but I was wondering if that's just because I switched the sampling rate from 6 seconds to 1 second (compared to the previous flights). You'll notice in the first file that other EGTs exhibit the sawtooth later on in the data as well albeit not quite as much as EGT #2. You thinking intake or exhaust valve?

https://www.savvyanalysis.com/flight/3461969/c1763104-2558-4ee7-84aa-d1a984f7534f https://www.savvyanalysis.com/flight/3461967/0f532371-5415-4a7e-90cd-030e8fdfbe4b https://www.savvyanalysis.com/flight/3461965/4c99944c-2c58-4632-8785-c5452df8cd1e These all had the issue. Thank you. -Evan

Hey Guys, So recently I have been having an issue where the IO-360-A1A starts very nicely, but then the engine stumbles every few seconds at idle with occasional popping/quiet backfire. Tried lean, rich, fuel pump...no adjustments made with the fuel seemed to help. The issue goes away when adding power (>~1800RPM) but when I bring it back down, the stumbling/backfiring starts happening again. All EGTs and CHTs looked normal throughout. I checked all the bolts on the intake to make sure they were tight, which they were. I downloaded the data from the JPI and couldn't spot any issues. Before I go pulling/inspecting fuel injectors and spark plugs, I was hoping someone might be able to spot the issue in the data... NOTE: I noticed the issue on 9/8/19 so all the data from that date forward had the issue. For the U190915A.JPI file, I changed the sampling rate of the JPI down to 1 sec. Thanks in advance! U190915.JPI U190915A.JPI

Thanks for you insight!

So is anyone using the Phillip's Victory 100AW? Says it's a replacement for the Aeroshell 100 plus. A box of the Victory 100AW is $20 cheaper per case than the Aeroshell

Thanks for the info!

Checked out 'All American Aircraft.' If I were to go through them, is there is a Broker fee? Or is the sales price what I'd pay? Thanks!

Thank you for the information. Just trying to learn the market and would eventually like to own my own if given the opportunity. Thanks.

Just curious, how much did you end up selling it for? Thanks.