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Airflow Performance help

GaryK

Well Known Member
Friend
The title may be a little misleading but I'm stuck on thinking my issue is the fuel system. My RV10 has been pretty much trouble free for 400 hours. 4 weeks ago I noticed on climb out it was rough (so was cruise), the number 1 EGT was higher than normal and erratic. moving up and down. Figured I had a nozzle that was partially clogged. Cleaned the injector and everything was back to normal for approx. 25 hours. Now my number 6 EGT is higher than normal by 75 - 100 degrees. I have the same engine roughness. Figured it was the same thing so cleaned the injector. This time it did not help. Called AP and asked them for suggestions. The next step was to test the flow divider, nothing was out of the ordinary, all 6 measuring cups were close to exactly the same. I though maybe that would have cleared out any dirt so took it up again but had the same roughness and higher EGT on number 6.

I'm looking for suggestions on what else I could try. Can't help but think I've overlooked something obvious as I'm fixated on the fuel system.

Here's what I've done so far and a little history.

1. All injectors were cleaned at annual (approx. 70 hours ago)
2. The roughness happens in cruise and higher power settings (20" - full power)
3. When I power back to 19" or less the engine runs very smooth like it always did.
4. I don't believe it's an ignition problem, roughness is the same on conventional mag and LS.
5. Cylinder temp on #6 is close to where it always was.
6. Run up is normal with no sign of roughness
7. The Flow Divider test has you run the fuel pump mixture rich, Throttle at idle after clearing the lines of air. That test showed equal flow but it's at idle flow not high power.
8. I switched the #6 injector nozzle with another and have the same issue on #6.

I was thinking the next logical step would be to remove the flow divider and clean per the service manual.

Any suggestions would be most welcome.

Gary
 
Check compression on #6. Could be a valve issue. I wouldn't assume fuel or spark until you check the fundamentals. If compression is ok, change both plugs in #6 as well.
 
Have you ruled out induction leaks? I believe the symptom you describe fits the bill.
 
I agree with Ross, check the fundamentals. If ou have engine data you should download it and see if you can see any issues. At 400 hours stuck valves are not out of the question although this typically shows up with lower temps.
You did not mention your ignition system but this would be about the time you might have issues with your mags and one plug not firing could cause some roughness and would drive up EGT temps.
 
Definitely check for intake leaks, especially the gaskets if you have never changed them. It is clearly running leaner, and with it doing the same on both ignitions, you have eliminated plugs and wires breaking down at high power.

Since you cleaned the injector once and it fixed it, there may still be some junk in that nozzle line. I would clean it before I would pull the divider.

Vic
 
Before any of this I would verify that the #6 EGT is on the #6 cylinder. If you cleaned #6 but the probe is actually on #4, that could be the problem.
 
Thanks for all the suggestions.

Vic.. The injector that was giving me problems last time was #1, this time it's #6.

I'll check the intake gasket tomorrow, don't see any stains but you never know. Will also check compression.

Jesse...I did the heat gun thing just to verify it was indeed #6.

Gary
 
#1 vs #6 issue may not be related. In addition to the segestions offered a leaking exhaust valve can cause this,do a compression check and listen for air from corresponding exhaust pipe
 
Gary,
I don't have any insight to your specific problem, but do have a recommendation for figuring it out. I am a huge fan of Savvy Analysis, Mike Bush's company, for assistance in diagnosing engine issues.

My first experience with them was when I owned a Lancair Super ES. I was experiencing a very random and very subtle engine miss while in cruise. Runup was always ok and miss was so random my AP couldn't find the issue. His suggestion was to "start with the fuel pump". To expensive of a "guess" for me.

Signed up for Savvy Analysis (https://savvyanalysis.com/Pro) flew their recommended profile, dowloaded the data from engine analyzer, uploaded file to Savvy for their review.

Came back with "top plug on #1 cylinder is bad". I replace this single plug (though AP said they were fine) and it never ran better.

Not positive they can solve your problem as easy, but they were a HUGE help for me in this case and two other issues with my Mooney plane. They saved me lot's of money and time with their expertise.

Hope this helps. Good luck tracking down the issue!!
 
If you are having the issue at WOT, it's unlikely an intake gasket leak since there is little or no pressure differential present under those conditions. As some others have mentioned, intake leaks usually cause far more lean out at idle/ part throttle where delta P is higher and mass flow lower.

Intake gasket is easy to check of course...
 
running fine again

Thanks to all who responded with ideas.

Went back to basics per some suggestions.
The compression test was fine 77/80.
The intake gasket on #6 had a small tear but outside of the sealing flange, changed it anyway just in case.
The #6 and #4 lower plugs (REM38E) had good amounts of lead deposits, cleaned them really well. They only have 60 hours or so on them. Need to lean even more aggressively on the ground.

Not sure if it was the lower plugs or the gasket but the engine is running perfectly again.

I'll add checking the lower plugs at every oil change since the cowl is off anyway,. The top plugs were perfect as they usually are with the LS ignition.

Thanks again for all the suggestions.

Gary
 
I had a similar issue - my finding was the little screw in thingy for the spark plug lead was loose at the plug end. I'm talking about the thing inside that looks like a spring and kinda screws in to the core of the plug wire.
 
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