Engine Stumbles Inflight - What Caused it?

Welcome back to the channel, aviators! In this video, we tackle an unexpected engine stumble that occurred on our last flight. Join us as we troubleshoot and diagnose the issue with the help of Savvy Aviation, ElectroAir, and our AME Chris. We'll walk through our detailed engine analysis, in-flight tests, and the steps taken to identify and replace a weak / faulty spark plug. Get ready for an in-depth look at aviation maintenance, engine performance monitoring, and the importance of meticulous pre-flight checks. Don't forget to like, comment, and subscribe for more aviation adventures!

How to troubleshoot aircraft engine issues
Fixing engine stumble in general aviation
Step-by-step aircraft engine diagnostics
Diagnosing spark plug problems in planes
Savvy Aviation engine analysis review
How to perform an in-flight engine test
Replacing spark plugs in an aircraft engine
Electronic ignition vs. traditional magneto
Engine performance monitoring for pilots
In-depth aircraft maintenance procedures

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⚠️ NOTE: These videos are edited for time and entertainment. Editing removes context and can remove safety checklists in the interest of time. Do not use these videos for, or in lieu of flight training.⚠️

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[Ea-Nasir_Copper_Co]

Oh, that's frustrating. Intermittent faults are a pain in the neck.

[midhudsonmarketing]

Good luck with this intermittent problem. Hope you've solved it. – Marilyn

[brianr]

Had a similar issue and was a cracked spark plug like others have said. I did switch 4 years ago to Tempest fine wire plugs and highly recommend them. They are expensive but last much much much longer. There are so many benefits! From leaning, easier starts, no fouling, more complete ignition and more! Worth every penny!

[mandrake]

Hi Glen! Just FYI. On my o300 I had a similar stumble that was intermittent. Eventually narrowed it down to a cracked spark plug....that would test okay....but under heat and stress every now and then would hiccup. Changed out that plug and smooth running

[barrysuomu]

I had a stumble on my C85. Ran great for 2 years then a stumble. I always run 1 oz Marvel Mystery Oil in 20 litres of fuel. Plugs are always clean and I check the spark plug resistance every time they are out. 500 to 5000 ohms is a good plug. I decided to try MMO in the oil. I now run with 1 oz MMO per litre of oil. Never again has it stumbled (over 100hrs). Plus I also use Phillips X/C 20W50. Great job troubleshooting!

[paulschannel]

I enjoy your videos, especially the troubleshooting and maintenance vids. Like the previous comment... intermittent problems are the worst!

[beverlynoddle]

Have followed your journey from the beginning. Hoped to see you today (Aug 10, 2024) at Edenvale Aerodrome at Meeting of the Classics - Cars and aircraft. 😢

[WolfPilot]

Good video Glen. Having that in depth understanding about whats going on under the cowling is ESSENTIAL to diagnosing these issues.

[MayhemCanuck]

Great start to troubleshooting, I work automotive and intermittent issue are such a pain with new cars. Starting with basic stuff like you did in most cases solves the issue even though you may not see the root cause during the diagnosis.
A white leaner plug compared to the rest is always a bit of a warning sign, you can eliminate a carburetor issue as that's the common feed for fuel for all six but since they all have individual runners you would think that a leak in the intake on that cylinder was the cause, but that would be all the time and not intermittent. That only leave the ignition system. hope its all fixed up :)

[GoingGreenMom]

Glad he found something and hope it works! Stay safe!

[marksmith]

Cool channel. I enjoy the thought process (of elimination). Had carb ice on final ever forget carb heat again

[StraightTail]

In a previous airplane I had I had the lightspeed electronic ignition with a dynon. I kept getting a stumble it scared me since we couldn’t troubleshoot the issue all the way. Took off the lightspeed and put a mag back on and never had any issues.

[fastbackflying]

Great Video again.

If the problem returns and you don't think it was a plug I would recommend a borescope inspection of the cylinders to check valves and ensure no burnt or damaged exhaust valves.

Sticking valves as you mentioned is also an issue and can start with intermittent stumbles. A close inspection to ensure the valves all move freely in their guides could be prudent.

I don't know if you use MOGAS at all but it now appears to all have ethonal regardless of grade so unwanted moisture content in fuel is an issue.

All the best and happy tailwinds.

[oreally]

I fully agree I wouldn't tolerate any stuttering. 😊 Just like a car on the ground, we ( people in general) have to stay on top of our machines.

[cgtbrad]

I've had this with a sticking valve. If that's what it is, it will typically be also be apparent shortly after start up (rough running) and then smooth out as the engine warms up. I've chased that with one of my cylinders have it reamed twice now. Very recently I've had two occurrences of rough running at top of descent if I reduce power and rpm. Upon inspection of my engine monitor data that one cylinder clearly has a noted drop in EGT at the times it ran rough. Getting estimates on replacing/overhauling that cylinder. Nothing like a rough running engine in flight to pucker you up!

[davecoleman]

An indication of a weak mixture on the new cylinder screams to me an air leak
With the engine running spray carb cleaner round the new jug if you hear an increase in engine speed you have diagnosed your problem
(Seating of new jug in engine casing ) ?
Great video

[AW-fbhr]

I'm no pilot, no nothing about plans, but still watching all this with rapt attention and wondering why can't you test the engine on the ground?

[fallingwickets]

safe travels....must be bit concerning

[andersonomo]

The only thing more frustrating than an intermittent fault is an inconsistent intermittent fault! I just about went nuts when a major new packing machine was installed at work and every time I did the prescribed steps to start it up it did something different. The machine was new to us and new to the technicians who installed it, and three different suppliers were involved, so lots of finger pointing! There was no blood and nobody died but it took it's toll!

[GeezerGeekPilot]

Nice video and troubleshooting, Glen. I also have the ElectroAir on my DA40. One question: when you uploaded the engine data to Savvy from the morning's stumble run, did those graphs show anything? Suggestion: if you do see the stumbles again, maybe go to real mag for a while, then EIS for a while (recording your engine data)... that may help further isolate the phenomena. Keep up the great postings! Thanks. Wayne (DA40 KSBA)