M20C cruise vibration

[LucasC]

Got the bird back from maintenance (OH Mags, fuel sender gaskets, etc etc and while on return trip home I forgot to lean out engine after climb for a while.  When I finally realized my newbie mistake and pulled the mixture back I have a vibration now.  Took her out for a spin today and same thing.  Runs smooth on climb but as soon as I pull mixture back I get the engine vibration again.  Any ideas? What's the fouled spark plug procedure on a carbureted mooney?

Thanks

Luke

[lifendet]

How much are you leaning? After leaning and feeling the vibration how close to full mixture did you give it to stop the vibration? Do you have any engine monitoring equipment?

Sent from my SM-G955U using Tapatalk

[LucasC]

1 minute ago, lifendet said:

How much are you leaning? After leaning and feeling the vibration how close to full mixture did you give it to stop the vibration? Do you have any engine monitoring equipment?

Sent from my SM-G955U using Tapatalk
 

She is about as old school as old school gets so no engine monitors or anything like that. 

[rbridges]

Is it passing the mag check during run-up?

[LucasC]

35 minutes ago, rbridges said:

Is it passing the mag check during run-up?

Yes the mag check is great. Been real cold here lately. 0-10 degrees f on ground. 1st winter with her and only acts up when i lean her out. 

[LucasC]

I will play with the mixture more next time im up. Just been so cold i dont wanna cool her off to much. Prob being to cautious. 

[mike20papa]

Sounds like you have your engine leaned to "stumbling lean". Normal vibration when leaned excessively.

Recommend you familiarize yourself with "the red knob" on the ground.  Especially if it is so cold, no possibility of overheating cylinders.  Start up, then begin backing out, leaning until you continue to get a smooth idle at 1500rpm.  reduce throttle to 1000rpm. Fine tune mixture to control power for taxi.  This approx. mixture setting is "lean for taxi".   If all goes well, I'd say you have functioning carb. and engine controls.  

Being so cold, the ability to "lean as normal" at altitude maybe not be SOP.  With air so cold/dense a richer mixture maybe required.  

[rbridges]

55 minutes ago, LucasC said:

Yes the mag check is great. Been real cold here lately. 0-10 degrees f on ground. 1st winter with her and only acts up when i lean her out. 

what about carb heat?  I had a situation where the carb heat was connected wrong, so it was always open.  It would stumble really bad when I leaned it.

[LucasC]

1 minute ago, rbridges said:

what about carb heat?  I had a situation where the carb heat was connected wrong, so it was always open.  It would stumble really bad when I leaned it.

Carb heat check at run-up is correct. 

[LucasC]

mike20papa i will try that. Maybe just so damn cold. Cyl head temp is always at bottom of green or barely not in the green. 

[orionflt]

Lucas,

I have the same basic airplane as you with the exception that I have added an engine monitor. we flew out to Cambridge Md this weekend and I could not keep my cylinders much above 250 except for number 3, that was close to 300. my dog house is so tight that even in the summer I'm in the low 300s. I have never gotten any vibrations when leaned out unless I over lean and the engine starts running rough. because everything is running well when rich, I wonder if you might have a small intake leak that is more prevalent when its cold out.

looks like you are up in NY, that's not too far away from me (KUKT) Quakertown. if you want to come down some weekend we can look your plane over and see if we can find out what is going on.

Brian 

[Hank]

My C only begins running rough when I lean it past peak EGT. Since resurrecting my doghouse and carb heat apparatus, I can generally get about 25° LOP at altitude before it starts.

Note that I have only the factory single-point EGT. 

When it's extra cold out, my Owners Manual says to add 1% to the power shown in the Performance Tables for every 10°F that temps are above ISA. The engine will make more power at a given MP / RPM combo, so you won't be able to lean as far before getting rough.

Check where the vibration starts as you lean compared to where your EGT peaks. It doesn't matter if your gage has no numbers, each mark is 25°F. Lean to.peak, then enrichen. Real old school is lean to rough, enrichen til smooth . . . .

[Jim Peace]

4 hours ago, rbridges said:

I had a situation where the carb heat was connected wrong, so it was always open. 

I am shocked and in disbelief on that.....LOL just kidding....its the norm for many of todays shops for many reasons

[DXB]

Obligatory obnoxious post that someone will make eventually - might as well be me .  A modern engine monitor can be used to sort these issues with a high degree of certainty within minutes by an owner with pretty basic knowledge.  Induction leak? Ignition system defect?  Which mag? Which cylinder? Which plug?  Not an engine issue at all?  

 

4 hours ago, rbridges said:

what about carb heat?  I had a situation where the carb heat was connected wrong, so it was always open.  It would stumble really bad when I leaned it.

Shouldn't open carb heat give you stumbling full rich at low rpms?  I would think leaning would help.

[Hank]

18 minutes ago, DXB said:

Shouldn't open carb heat give you stumbling full rich at low rpms?  I would think leaning would help.

Carb heat will make the mixture richer at any throttle & RPM setting, by reducing the amount of air coming in (engine intake is a fixed volume, but warm air is lower density). If too rich for conditions it may stumble; if too lean for the power setting, it WILL run rough with less power than desired. 

[LucasC]

When the weather cooperates i will try a few things. Looking at 16in snow up here tonight.  will get back to you all with results. 

[rbridges]

4 hours ago, DXB said:

 

 

Shouldn't open carb heat give you stumbling full rich at low rpms?  I would think leaning would help.

duh.  that's right.  I had to lean it when that happened.  I was thinking more air, more fuel, but it's actually less dense air, less fuel.

[carusoam]

Luke,

you should have a single EGT gauge as a standard instrument.  It may not have any numbers on it and the calibration knob is on its front...

Verify if you have it, we can discuss how to use it...

It may be its installation and how cold it is...

What procedure were you using for leaning? Lean til rough, then increase the mixture?

Best regards,

-a-

[LucasC]

3 hours ago, carusoam said:

Luke,

you should have a single EGT gauge as a standard instrument.  It may not have any numbers on it and the calibration knob is on its front...

Verify if you have it, we can discuss how to use it...

It may be its installation and how cold it is...

What procedure were you using for leaning? Lean til rough, then increase the mixture?

Best regards,

-a-

Yes lean till rough then increase mixture. This seems like a vibration to me not engine roughness but thats just me. No egt on this plane just oil temp and cyl temp. 

[moodychief]

Is your prop balanced?  Do you have 2 or 3-bladed prop?

[Hank]

1 hour ago, LucasC said:

Yes lean till rough then increase mixture. This seems like a vibration to me not engine roughness but thats just me. No egt on this plane just oil temp and cyl temp. 

Never seen a plane with no EGT at all . . . Does it still eventually smooth out as you richen it?

[orionflt]

4 hours ago, Hank said:

Never seen a plane with no EGT at all . . . Does it still eventually smooth out as you richen it?

mine didn't have it until I installed my engine monitor.

Brian

[LucasC]

6 hours ago, moodychief said:

Is your prop balanced?  Do you have 2 or 3-bladed prop?

I had some prop work done in sept. Sent out to prop shop to have a ding blended out. I was thinking it may be that. Im going to play with the mixture next time im up and a few other checks then im going to get it dynamically balanced. Just cant remember feeling it so bad.

 

[LucasC]

6 hours ago, Hank said:

Never seen a plane with no EGT at all . . . Does it still eventually smooth out as you richen it?

This is my 3rd plane. Only my sundowner had egt. My older 172 also did not. I did find with my beechcraft that if i leaned with the egt or the old school way they were pretty close. 

[carusoam]

Most Mooneys got an Alcor early on... like this one...

https://www.ebay.com/i/202526776637?chn=ps&ul_ref=https%3A%2F%2Frover.ebay.com%2Frover%2F1%2F711-117182-37290-0%2F2%3Fmpre%3Dhttps%253A%252F%252Fwww.ebay.com%252Fi%252F202526776637%253Fchn%253Dps%26itemid%3D202526776637%26targetid%3D596465943068%26device%3Dt%26adtype%3Dpla%26googleloc%3D9004025%26poi%3D%26campaignid%3D1689407489%26adgroupid%3D74365778308%26rlsatarget%3Dpla-596465943068%26abcId%3D1140476%26merchantid%3D8050544%26gclid%3DEAIaIQobChMI3fOQrPG64AIVmq_ICh0xgQ_qEAQYBCABEgLOBvD_BwE%26srcrot%3D711-117182-37290-0%26rvr_id%3D1857960148740%26rvr_ts%3Deb4956581680a990b344caddffee6a5c

 

They are inexpensive, and self powered, easy to learn...

Adding a carb temp gauge is more of a challenge... also important to be familiar with... why and how...

Best regards,

-a-