Angry engine after restart

[Joe Larussa]

I’ve noticed that after landing and refueling then restarting my engine it seems unhappy. Runs a little rough and pops and farts a little. All monitors are normal. I power up for take off and it purrs like a kitten. It does not like to idle when it’s hot. Thoughts?

[PT20J]

Poor idle but running well at higher power can be caused by an induction leak. Extra air leans out mixture at idle, but if the leak is small it won’t have much effect at higher fuel flows. 

Skip

[Andy95W]

Does leaning the mixture help at idle?

Skip noted that an air leak could cause the roughness.  I’ve seen that and also the opposite when the engine is really warm- it doesn’t need as much fuel to idle when hot.

[Marauder]

When my engine did this, I look really carefully at the engine analyzer and found that I could actually see one cylinder EGT was cycling with the roughness. It was an induction leak.


Sent from my iPad using Tapatalk Pro

[ArtVandelay]

If I read you post correctly, this is a problem trying to run idle after a hot start…this is normal. This is the fuel boiling in the hot fuel lines. Try running engine at higher RPMs to get more cool fuel through the lines.

[Ragsf15e]

7 minutes ago, ArtVandelay said:

If I read you post correctly, this is a problem trying to run idle after a hot start…this is normal. This is the fuel boiling in the hot fuel lines. Try running engine at higher RPMs to get more cool fuel through the lines.

I agree, but this roughness should only last ~30” or so until you get cool fuel in the lines.  If it keeps doing it during taxi at idle rpm, induction leak or sniffle valve should be looked at.

[Vance Harral]

58 minutes ago, Ragsf15e said:

I agree, but this roughness should only last ~30” or so until you get cool fuel in the lines.

Depends on how hot things are.  It's not unusual for the heat soaking off the cylinders and in the engine compartment to cause poor flow in the fuel lines at idle power and taxi speeds, for much longer than 30 seconds.  The IO-360-A1A in our M20F pops and gripes like this on hot (or even warm) days, during the entire taxi from the fuel pump back to the hangar after flying (we have a post-flight fuel up policy in our partnership).  It doesn't have an induction leak - no other signs of one, anyway - it's just "the way things are".  It's been doing it since we bought it in 2004.

[jaylw314]

22 minutes ago, Vance Harral said:

Depends on how hot things are.  It's not unusual for the heat soaking off the cylinders and in the engine compartment to cause poor flow in the fuel lines at idle power and taxi speeds, for much longer than 30 seconds.  The IO-360-A1A in our M20F pops and gripes like this on hot (or even warm) days, during the entire taxi from the fuel pump back to the hangar after flying (we have a post-flight fuel up policy in our partnership).  It doesn't have an induction leak - no other signs of one, anyway - it's just "the way things are".  It's been doing it since we bought it in 2004.

I have not had that occur in hot weather up to 100deg F.   After a heat-soaked hot start, the engine will stumble for around 10-15 seconds, but as long as you taxi at 1000 rpm, it returns to normal afterwards.

As an aside, NEVER land at Fresno Executive during the afternoon in summer, it is absolutely brutal!   My wife resisted learning how to use the disposable toilets, but after that landing, she changed her mind!

 

[RobertGary1]

Yes normal. Just until the near boiling fuel makes its way through the lines.

 

-Robert

[Ragsf15e]

41 minutes ago, Vance Harral said:

Depends on how hot things are.  It's not unusual for the heat soaking off the cylinders and in the engine compartment to cause poor flow in the fuel lines at idle power and taxi speeds, for much longer than 30 seconds.  The IO-360-A1A in our M20F pops and gripes like this on hot (or even warm) days, during the entire taxi from the fuel pump back to the hangar after flying (we have a post-flight fuel up policy in our partnership).  It doesn't have an induction leak - no other signs of one, anyway - it's just "the way things are".  It's been doing it since we bought it in 2004.

I’ve got an F too and haven’t had the same experience.  They are all a little different, but mine runs smooth at 1000rpm after initially working through the hot fuel in the lines.

[ArtVandelay]

Pro tip: open cowl flaps when on a approach to landing, will cool the engine a bit better at reduced speeds. Also running at little higher RPMs (1200-1300) after start with cowl flaps open will also force more cool air as well, as mentioned above should only have to do this for 15-30 seconds and then can drop down to 1000 RPMs.

[A64Pilot]

1 hour ago, ArtVandelay said:

Pro tip: open cowl flaps when on a approach to landing, will cool the engine a bit better at reduced speeds. Also running at little higher RPMs (1200-1300) after start with cowl flaps open will also force more cool air as well, as mentioned above should only have to do this for 15-30 seconds and then can drop down to 1000 RPMs.

Cowl flaps on final also puts you in a position for a surprised go -around too.

[Vance Harral]

On 3/25/2022 at 11:51 AM, jaylw314 said:

I have not had that occur in hot weather up to 100deg F.

On 3/25/2022 at 12:11 PM, Ragsf15e said:

I’ve got an F too and haven’t had the same experience.

Those data points are appreciated, but I'm not sure what to say about it.  It's a common occurrence at my home drome, and not just in my Mooney, but other fuel-injected airplanes.

One possibility is all of us have small induction leaks, and I'm not arrogant enough to rule that out entirely.  But induction leaks are relatively straightforward to check for in flight (see https://resources.savvyaviation.com/in-flight-diagnostics/), and my airplane doesn't exhibit the differential EGT delta discussed there.

The only other thing that comes to mind is that my home drome is 5050' MSL, higher than many of the participants here on the forums.  The air is less dense here, and therefore less capable of cooling, but I freely admit that's kind of a thin argument.  Might carry more weight if I was in Leadville or similar, but mile high isn't *that* high.

All I can say is that I'm pretty confident a bit of popping and griping from a fuel-injected engine whose cylinder feed lines run right over the top of the cylinder, while idling along the taxiway at lower power, even for extended periods of time, doesn't strike me as a "this is unsafe and must be fixed" kind of problem.

[ilovecornfields]

On 3/25/2022 at 10:51 AM, jaylw314 said:

I have not had that occur in hot weather up to 100deg F.   After a heat-soaked hot start, the engine will stumble for around 10-15 seconds, but as long as you taxi at 1000 rpm, it returns to normal afterwards.

As an aside, NEVER land at Fresno Executive during the afternoon in summer, it is absolutely brutal!   My wife resisted learning how to use the disposable toilets, but after that landing, she changed her mind!

 

Bullhead City, AZ in July had the same effect for our family.

[jaylw314]

1 hour ago, Vance Harral said:

Those data points are appreciated, but I'm not sure what to say about it.  It's a common occurrence at my home drome, and not just in my Mooney, but other fuel-injected airplanes.

One possibility is all of us have small induction leaks, and I'm not arrogant enough to rule that out entirely.  But induction leaks are relatively straightforward to check for in flight (see https://resources.savvyaviation.com/in-flight-diagnostics/), and my airplane doesn't exhibit the differential EGT delta discussed there.

The only other thing that comes to mind is that my home drome is 5050' MSL, higher than many of the participants here on the forums.  The air is less dense here, and therefore less capable of cooling, but I freely admit that's kind of a thin argument.  Might carry more weight if I was in Leadville or similar, but mile high isn't *that* high.

All I can say is that I'm pretty confident a bit of popping and griping from a fuel-injected engine whose cylinder feed lines run right over the top of the cylinder, while idling along the taxiway at lower power, even for extended periods of time, doesn't strike me as a "this is unsafe and must be fixed" kind of problem.

I dunno, 5000' does sound like a significant factor.  Is your mechanic at the same altitude?  That could affect your idle throttle/mixture setting?

[eman1200]

….Runs a little rough and pops and farts a little…

If this is an indication of an issue, I better get myself checked out asap!

[Vance Harral]

58 minutes ago, jaylw314 said:

I dunno, 5000' does sound like a significant factor.  Is your mechanic at the same altitude?  That could affect your idle throttle/mixture setting?

This particular airplane has lived "at altitude" for about 20 years, even the previous owner lived in the Utah high country.  I'm not concerned the fuel servo isn't set up properly if that's what you're getting at.  In particular, I have no desire for the fuel servo's idle adjustments to be set up more lean than they are, just because the home 'drome is 5050 MSL.  I want it to idle well at sea level, and it's simple to lean (aggressively) for taxi at home, which we do.

[Hank]

I lean aggressively for taxi everywhere. At home, <1000msl at three fields for the last 14 years, mixture is generally 3/4 travel toward ICO while taxiing around, even before I leave the runway. My first Cessna flight after several years of Mooney ownership, I did the same and the engine quit on the runway . . . .