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!
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!