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  #1  
Old 01-28-2018, 04:13 PM
N23WL N23WL is offline
 
Join Date: May 2017
Location: NE FL
Posts: 18
Default Engine missing - out of ideas

Consultation: RV9a with a TMX-360 Air Flow fuel injection, dual e-Mags, @ about 300 hrs. TT engine and airframe. About four months ago it began to miss occasionally on decent and lower RPM at operating temperature at or > 155-170 degrees F. The condition has continued and increased to the point that on let-down to pattern altitude, I am afraid to let the RPM drop below 1,000. To save many of the diagnostics questions, here is additional information.
Key points:
Runs perfectly below oil temperature 155 degrees and above 100 degrees until it starts to miss
Use only 100 LL
The inline filter was never installed but I do have good pressure distally at the air filter
Condition is worsening as time goes on.
Mixture setting and boost pump do not play a part
Loaner set of new E-mags are properly installed/timed - doesn?t change the problem.
Old plugs never gave a hint if a problem. Replaced with iridium
I don?t know - but don?t really suspect a stuck exhaust valve
Compressions all in the mid/high seventies.
More: Mag check revealed normal loss during runup, continues to run with the master off if the RPM is above 900 RPM. Engine will stop if the mags are placed in the test position below 900 RPM. E-mags (Company) have check my set and found them to be serviceable and even loaned me a set for testing. The leads are new and the plus are new and iridium.
All grounds have been tested and secure. The master and solenoid have been changed because the cost was low based upon the theory that the solenoid (internally grounded) might be the culprit. Actually, by chance or design worked for three hours flight then the problem continued.
Voltage: Good battery 13.4-13.8 at the post. 12.6 at the firewall ground. 12.3 at the master. Full load, i.e., master, mags, radios, transponders, cooling fans, etc. showed a drop only to 12.1 volts.
The alternator checked out while cool and continues to leave the battery charged after running.
I have not checked the fuel injectors.
Thought about the diaphragm on the fuel pump but again, the pressure seems good and the boost pump doesn?t help. Mixture doesn?t change the problem.
I would appreciate discussion, questions and any ideas anyone has.

Thanks!
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  #2  
Old 01-28-2018, 05:03 PM
Mark Dickens's Avatar
Mark Dickens Mark Dickens is offline
 
Join Date: Apr 2012
Location: Collierville, TN (KFYE)
Posts: 1,433
Default

Just a thought, and I'm sure more knowledgeable folks will be along soon, but have you checked for intake leaks? What does your EGT do when the engine starts missing? Lastly, do you have log data to analyze?
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  #3  
Old 01-28-2018, 06:02 PM
N23WL N23WL is offline
 
Join Date: May 2017
Location: NE FL
Posts: 18
Default

Mark,

Thanks for responding. Your question is good but I can't answer specifically because my GRT CHT & EGT is unreliable. I ran the engine from startup to operating while conducting a series of IR temperature readings on all cylinders; This includes both at the exhaust manifold and on the cylinder walls.

The temperatures, though not true as they would be from the probes were entirely consistent and within the norms from the start of the test when the engine was cold until full operating temperature. I too was looking for an inconsistency in a cylinder or exhaust temperatures but didn't find one.

That was a good question and I am sorry I did not include that information in my initial post.

Thanks!
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  #4  
Old 01-28-2018, 06:39 PM
E. D. Eliot E. D. Eliot is offline
 
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Location: San Pedro
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Default Thoughts

I have zero experience with Lycoming but a fair amount with auto engines - obviously, I am not an expert but - I'd first change the 'new' plugs out for another new set. Sometimes, you will get a bad plug right of the box. Next, I'd ohm out your spark plug wires and replace all of them if one of them is bad. These can deteriorate with time on any engine. Probably would check for sticking valve first. Please let us all know which action solved this problem - good luck.
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  #5  
Old 01-28-2018, 06:54 PM
DHeal DHeal is offline
 
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Location: Windsor, California
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I had a Lyc 0-360 in my Starduster Too that had a strange miss. It went away after I checked the valve lash and adjusted the push rod lengths to meet spec. Its an easy check.
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  #6  
Old 01-28-2018, 08:20 PM
VA Maule VA Maule is offline
 
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Location: Bucking ham, Virginia
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Has the engine been run and then set idle ( put aside during the build) for an extended period of time? If so it's possible to be the dreaded Lycoming cam & tappet rust . I hope I'm wrong but if performance gets worse at an accelerating pace ( just 5-10 flight hours) this could be it . An oil filter inspection in a few more hours can confirm or exclude .
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  #7  
Old 01-28-2018, 08:28 PM
tim2542 tim2542 is offline
 
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Location: Redding,Ca
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You are really handicapped not having the EIS working properly. The info you could download and analyze would greatly simplify your diagnostics.
I think the suggestion to check your valve lash is a good one based on what you?ve told us.
Good luck
Tim Andres
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  #8  
Old 01-29-2018, 06:44 AM
N23WL N23WL is offline
 
Join Date: May 2017
Location: NE FL
Posts: 18
Default TMX 160 engine missing

I want to thank everyone for the suggestions. I have the suggestions in hand and will move forward in this order.

1. Check the valve lash and adjust the push rod lengths to meet specifications. I had not thought of that.
2. I have checked the plugs and plug wires and they pass resistance testing
3. I am considering cleaning the injectors.
4. The engine has never been idle for any length of time but I'll consult a pro on the rust issue.

I will report back

Thank you for taking the time to help me through this.
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  #9  
Old 01-29-2018, 07:28 AM
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Zuldarin Zuldarin is offline
 
Join Date: Mar 2013
Location: Snoqualmie, wa
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My 9A does something that I assume is similar and its heat based. When coming in to the pattern on a hot day the engine will stumble a bit due to fuel flashing in the fuel lines. I was able to minimize this by shielding the fuel lines from exhaust heat but I have yet to completely eliminate it.

Do you have issues with the engine stumbling at idle on hot taxi's? I do.
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  #10  
Old 01-29-2018, 07:57 AM
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rv8ch rv8ch is offline
 
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Location: LSGY
Posts: 3,199
Default EIS

As Tim suggested, I'd call GRT and get the EIS working right. That will really help diagnosis.
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