O-200 engine stutter

DC34ME

DC34ME

Pre-takeoff checklist
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DC34ME
It is probably nothing but I have felt my O-200 stutter for a second or two on two different flights. Both flights were in the evening at 2000ft. and around 10-20 minutes into flight. The RPM would drop a few hundred for a second with no vibrations then back to 2500RPM. Both flights I had 12-14 gallons total, and checked for water before flying. OAT was in the 90's and engine temp was about 190 F. I assume it is just water or something in the fuel line. So what else may have caused this?

The engine is an O-200 overhauled 10 years ago by Mattituck, and has 400hrs SMOH and doesn't burn more than a 1qt of oil every 8 hours.

Thanks,

Mike
 
except for the "no vibrations" part I would think a stuck valve..
but the stuck valve I've felt on the O-540.. really vibrates..

intermittent mag grounding..?? bad P-lead?
 
And by no vibrations I mean nothing violent. Engines always have a vibration to them, and this loss of RPM didn't bring any worse a vibration than normal at 2300 RPM. Maybe I was too focused on the problem to notice, plus it happened so fast.

Could be I have first airplane jitters and every little thing makes me and my wallet scared!
 
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DC34ME said:
And by no vibrations I mean nothing violent. Engines always have a vibration to them, and this loss of RPM didn't bring any worse a vibration than normal at 2300 RPM. Maybe I was too focused on the problem to notice, plus it happened so fast.

Could be I have first airplane jitters and every little thing makes me and my wallet scared!
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Are you running autofuel? Could be a touch of vapor lock. Happened to my 150, once.

Ron Wanttaja
 
40 hrs a year means the plane sits alot. Fuel does strange things when it sits and leaves deposits around, these deposits can come loose and partially obstruct jets and metering pins, might pull the bowl off the carb and take a look and give it a cleaning. If you are full rich in those conditions, you could also be getting small bits of ice forming right upstream of the fuel port. You may try leaning it out and giving less fuel to evaporate and cool. Couple things to try anyway.
 
DC34ME said:
It is probably nothing but I have felt my O-200 stutter for a second or two on two different flights. Both flights were in the evening at 2000ft. and around 10-20 minutes into flight. The RPM would drop a few hundred for a second with no vibrations then back to 2500RPM. Both flights I had 12-14 gallons total, and checked for water before flying. OAT was in the 90's and engine temp was about 190 F. I assume it is just water or something in the fuel line. So what else may have caused this?

The engine is an O-200 overhauled 10 years ago by Mattituck, and has 400hrs SMOH and doesn't burn more than a 1qt of oil every 8 hours.

Thanks,

Mike
Click to expand...

Could be a valve trying to stick or weak valve springs. I've experienced both with similar symptoms.

Deb
 
DC34ME said:
It is probably nothing but I have felt my O-200 stutter for a second or two on two different flights. Both flights were in the evening at 2000ft. and around 10-20 minutes into flight. The RPM would drop a few hundred for a second with no vibrations then back to 2500RPM. Both flights I had 12-14 gallons total, and checked for water before flying. OAT was in the 90's and engine temp was about 190 F. I assume it is just water or something in the fuel line. So what else may have caused this?

The engine is an O-200 overhauled 10 years ago by Mattituck, and has 400hrs SMOH and doesn't burn more than a 1qt of oil every 8 hours.

Thanks,

Mike
Click to expand...

I've had something similar happen to me a couple of times in our C150 a few years back, although I would have called it a stumble not necessarily an RPM drop, we never could find anything wrong with it.

-Henri
 
i've had similar symptoms in a rental 182 and 172 when one or more plugs "loaded up" with lead deposits

once I made a precautionary landing in a 182 because i could not "lean it away"
had a mechanic check the plugs and he found both in one cylinder had a glob on them
 
The airplane sat for a year before I purchased it last month, and have now put over 15 hours on it in June alone. I do lean the mixture on the ground and in flight. I do not run autofuel but it does have the STC for it, and I'm sure it has been ran in the plane before.

Thanks for all the response!
 
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A little skip and a miss now and then is typical of the beast, because of the remote mounted carb, and poor fuel distribution. once in a while the fuel simply doesn't get to the cylinder.

I would inspect the rubber boots on the intake pipes, they will some times leak and cause this also.
 
The airplane sat for a year before I purchased it last month, and have now put over 15 hours on it in June alone. I do lean the mixture on the ground and in flight. I do not run autofuel but it does have the STC for it, and I'm sure it has been ran in the plane before.
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Mike: You might be getting lead buildup on the valve seats/stems. I also have an O-200. Mine is bad to get lead/carbon buildup on 100LL. I was using TCP in the fuel. When my mechanic told me the spark plugs looked like they were really running hot and I might want to cut down on the TCP, I quit using TCP. Within about three or four months, I had a stuck exhaust valve. Got that fixed. About 5 months later (at the annual) had another stuck valve. I went back to using TCP and have been running it for a year. No more valve problems so far.
 
I may try TCP, for $35 a qt. I get 16 fill ups worth at 2 ounces of TCP per 20 gallons of gas. I do fly a little rich on the mixture. I will get my mechanic to look at some things on the next oil change.
 
DC34ME said:
The airplane sat for a year before I purchased it last month, and have now put over 15 hours on it in June alone. I do lean the mixture on the ground and in flight. I do not run autofuel but it does have the STC for it, and I'm sure it has been ran in the plane before.

Thanks for all the response!
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Have you sumped the belly drain yet?
We had a C-150 sit on the ramp for over a year. The new owners drained all the fuel from the tanks (lots of water) and filled it up with 100LL. Still had lots of problems. Drained the tanks again but this time removed the belly drain plug...you would not believe the crap that came out of that drain...
You might also pull the fuel line in the engine compartment off (after turning off the fuel of course) and swab the inside to see if sometime in the past someone put Alky-laced auto fuel in it and the fuel line is coming apart. If you run a swab thru and ger ANY rubber bits you'll need to go from tank-to-carb and clean/replace as needed.

These may not be your problems but it gives you something else to look at.

Chris
 
Well I purchased some TCP yesterday, and a syringe. Filled the tanks with LL and added a little less TCP than the recommended dose. Fired up the old girl and flew to KRYY for dinner. Engine ran great for the 1.6 hour round trip. On the way home I was cleared over Hartsfield-Jackson at 4,500ft. that was cool.

So what are some of the risks with using TCP, other than spark plugs running hot?
 
So what are some of the risks with using TCP, other than spark plugs running hot?
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Mike:

I am not aware of any real downsides. The TCP does sometimes leave a white deposition that I notice from the carb drain, but that has never bothered anything that I know of. I plan to continue to use it.
 
And on it goes. One guy suggests fouled plugs, the others all suggest fuel issues. Fuel issues will cause serious RPM drops, sometimes total quiet. If there's enough water in the system to do that and the pilot didn't drain the sumps and strainer before flight, the engine would die and stay dead.

90% of all engine hassles are electrical. Ignition. A "few hundred RPM drop" sure sounds like a magneto that's taking a holiday once in a while. Magnetos will make far more trouble than a carb.

I know this engine wasn't doing it, but an O-200 stuttering or hesitating on takeoff can be caused by the carb spider being improperly mounted. The Marvel Schebler/Precision Airmotive carb doesn't like to be shaken and will spill fuel from the bowl vent (behind the venturi) into the carb throat and make the mixture rich and really uneven. The spider is supposed to have special rubber-centered washers above and below it, and the nuts are to be finger-tight, no more, and pinned there. Check the overhaul manual. This lets the spider and carb flex a lot to stop its shaking with the engine, and the intake rubber tubes need to be flexible, too, not old and hard.

Dan
 
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Dan Thomas said:
And on it goes. One guy suggests fouled plugs, the others all suggest fuel issues. Fuel issues will cause serious RPM drops, sometimes total quiet. If there's enough water in the system to do that and the pilot didn't drain the sumps and strainer before flight, the engine would die and stay dead.

90% of all engine hassles are electrical. Ignition. A "few hundred RPM drop" sure sounds like a magneto that's taking a holiday once in a while. Magnetos will make far more trouble than a carb.

I know this engine wasn't doing it, but an O-200 stuttering or hesitating on takeoff can be caused by the carb spider being improperly mounted. The Marvel Schebler/Precision Airmotive carb doesn't like to be shaken and will spill fuel from the bowl vent (behind the venturi) into the carb throat and make the mixture rich and really uneven. The spider is supposed to have special rubber-centered washers above and below it, and the nuts are to be finger-tight, no more, and pinned there. Check the overhaul manual. This lets the spider and carb flex a lot to stop its shaking with the engine, and the intake rubber tubes need to be flexible, too, not old and hard.

Dan
Click to expand...

and that looseness is what causes the intake boots to pull off the intake pipes and start a cylinder to run lean, and go to a lean miss fire
 
We run two C150'sa and an Ercoupe and have had similar experiences a number of times. Usually it is a sticking exhaust valve, and usually due to carbon/lead build up in the valve guide. Google "Rope Trick O-200" and
you will find how to clean/Ream the exhaust valve guides.

The new ECI titan O200 cylinders have a rotator to turn the exhaust valve and reduce buildup on the exhaust valve guides.

mitch
 
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