Engine roughness IO-540

[Kitch]

Climbing out today in the 206 get to 1000’ start to pull the power back to 25 I get to about 26 and get some roughness similar to carb ice or the primer not being locked. I immediately go back to full power and start to turn back. As soon as I go full power it smoothes right out. I pull it back again get to 26 same results rough again advance the power smoothes out. No issues with power reduction as we come around to land. Taxi clear do a mag check all checks out fine. Fuel flows where normal through the whole process. Taxi back out to do a lap in the pattern everything was fine. I sumped the tanks and belly before and after no signs of contamination. 800 SMOH Needless to say I’m a little bit confused. Spent an hour close to the airport the did 3 more T/O and landings without issue.

Thoughts or comments

 

[SixPapaCharlie]

Prop governor?

 

[Kitch]

Prop governer?

I’ll likely get flamed by someone for asking this…

Why would the prop gov cause a roughness that went away with full power applied ? For the record I’m not being argumentative just curious.

Prop cycled fine on the ground with no oil leaks etc.

 

[SixPapaCharlie]

I've spent the last month Comanche shopping.
One of the planes I looked at, the owner described something similar.

He said he spent a month trying to track down the issue and it turned out to be the prop governor.

I know very little about these engines yet but his Simptoms we're similar also thinking it might be an unlocked primer.

Here is his post that turned out to be the PG

 

[455 Bravo Uniform]

Engine monitor?

 

[Kitch]

Engine monitor?

G1000 Everything was in the green. Fuel flow, oil psi and temp. Just the slightest roughness when I started easing the power back. Did it twice in a row then cleared right up and was fine for the next 1.4

 

[Kitch]

I've spent the last month Comanche shopping.
One of the planes I looked at, the owner described something similar.

He said he spent a month trying to track down the issue and it turned out to be the prop governor.

I know very little about these engines yet but his Simptoms we're similar also thinking it might be an unlocked primer.

Here is his post that turned out to be the PG

View attachment 102416

Fuel injected so not the primer. Never lost enough power to stop climbing just a couple stumbles around 26” as soon as I pushed the throttle back in it cleared right up.

 

[Clip4]

I vote for induction leak.

 

[Kitch]

Let me throw this in the mix. As I was sitting on the ground waiting for oil temp to come up, and while taxiing I forgot to lean it out a bit like I normally do. Is it possible I was loaded up with fuel ?

Stuff like this makes me think about for hours after the fact…

 

[Kitch]

I vote for induction leak.

An induction leak would cause a rough idle if it would idle at all wouldn’t it ?

*not being argumentative just trying to talk it out

 

[sourdough44]

With ‘momentary engine roughness’ I’d at least look into & try to eliminate some simple stuff. I had some a while back on my injected IO-390.

The simple stuff is plugs & injectors to start with. In my case I inspected, then insured both were clean, I knew what cylinder with the monitor.

At times it can be that ‘slug’ of water, magnified when flying. If so it’s usually very momentary, then gone.

The age, condition of the engine can factor in, harness having issues can contribute.

For me, I ensure things were clean & clear, no problems since.

 

[Kitch]

Update.... Checked some simple things yesterday around lunch time talked to my A&P for awhile about it. Did a mag check at 1800 & 2300 everything ran perfectly for 2.4 so I guess the mystery continues...

Thanks for all the feedback !!!

 

[Dan Thomas]

Some systems go leaner when the power is reduced. If the spark is weak, this can produce roughness. Old Champion plugs, tired harness, mags needing new points and condensers.

So. When were those mags last off for inspection? Should be every 500 hours (Slick) or 400 (Bendix/TCM). Are the plugs the old Champions with the resistors that fail? Look down the connector bore and see if there's a slot in the contact. If so, they're poor plugs.

Watch the EGT as you reduce power a bit. If it doesn't fall, or if it rises, it's going lean as you pull the throttle back a little.

 

[Kitch]

Some systems go leaner when the power is reduced. If the spark is weak, this can produce roughness. Old Champion plugs, tired harness, mags needing new points and condensers.

So. When were those mags last off for inspection? Should be every 500 hours (Slick) or 400 (Bendix/TCM). Are the plugs the old Champions with the resistors that fail? Look down the connector bore and see if there's a slot in the contact. If so, they're poor plugs.

Watch the EGT as you reduce power a bit. If it doesn't fall, or if it rises, it's going lean as you pull the throttle back a little.

Great info Thank you !! I'll check these specific things. Last mag inspection was less the 250 hrs ago