I have a parallel valve Superior IO-360 in my RV-7. Vertical draft P/A Silverhawk fuel injection, 8.5:1 (180HP) pistons, dual Light Speed Plasma III ignitions, auto plugs (currently NGK BR8EIX), roller cam. Delivered new to me with 1 hour of dyno time in January, 2007. Sat pickled until first start in early June, this year.
The engine has always started easily, idles smoothly, with no signs of roughness on the ground other than the initial 1-2 seconds after it catches. Has only been run on 100LL. About 50 hours TTSN as of yesterday, oil changed regularly, burning about 1 quart in 25 hours now.
At about 5 hours of flight time, I was cruising at 6500', approximately 24 squared, leaned somewhat, when suddenly the engine started missing badly. After the initial panic and 180? turn back towards the airport (I was maybe 15 nm away at that point, airport is at sealevel) I noticed that CHT and EGT on #2 cylinder were dropping way off- it had gone completely cold. It was obvious that I was going to make the field, so I continued. Suddenly the cylinder came to life, as if nothing had ever happened. The symptoms reappeared as I was on downwind, but disappeared again by the time I was halfway through a 180 to final. Ran fine on the ground. My first thought was clogged injector, so I removed the line and the injector, checked for contamination. Found nothing. Reassembled, test flew, everything seemed fine.
A few hours of flight time later the problem reappeared, #2 cylinder again, once again it was only after I'd been flying for at least 15 minutes. Warm day, probably 80 degrees at altitude, but not scorching hot. That time it was intermittently less severe, but the cylinder eventually dropped off. During a beeline back to the airport it once again cured itself. Maddening, the worst type of problem to troubleshoot. This time I removed all the injectors, and, after calling Precision Airmotive, disassembled the flow divider to check for contamination. Found nothing. Ran fuel through the system with nozzles in glass jars which confirmed even flow. Swapped injector nozzles between #2 & #4 just in case, to rule that out. Reassembled, test-flew, everything was fine.
Yesterday, 35 hours after the last incident, the problem reappeared, intermittent in the air as always. Once again I returned to the airport and landed, only this time the problem continued intermittently on the ground. I ran it up to about 1500 rpm and watched the engine monitor. #2 would intermittently cut out (every few seconds) and when it did the EGT would drop precipitously. Once again I disassembled the fuel system from the flow divider on, but once again found nothing. I buttoned it up and test-ran it last night but didn't fly- it started and ran fine, all temps came up evenly.
Now I'm thinking about morning sickness, but I'm not sure what the symptoms are. It never happens at first start or when the engine is cold, but maybe that doesn't matter. What would one expect to see on an engine monitor? For what it's worth, I've checked compression, it's consistently 80/77 all around with a warm engine. Checked plugs, they looked fine everywhere yesterday. If an exhaust valve is sticking open, wouldn't EGTs go up instead of down?
I've spoken to a few local mechanics, but they don't have any ideas. I'm new to aircraft engines, but I've been working on ground-based engines my entire life, so I'm comfortable turning wrenches. I've read the description of the "rope trick" and I'm happy to do that if it makes sense.
Thanks in advance for any input!
The engine has always started easily, idles smoothly, with no signs of roughness on the ground other than the initial 1-2 seconds after it catches. Has only been run on 100LL. About 50 hours TTSN as of yesterday, oil changed regularly, burning about 1 quart in 25 hours now.
At about 5 hours of flight time, I was cruising at 6500', approximately 24 squared, leaned somewhat, when suddenly the engine started missing badly. After the initial panic and 180? turn back towards the airport (I was maybe 15 nm away at that point, airport is at sealevel) I noticed that CHT and EGT on #2 cylinder were dropping way off- it had gone completely cold. It was obvious that I was going to make the field, so I continued. Suddenly the cylinder came to life, as if nothing had ever happened. The symptoms reappeared as I was on downwind, but disappeared again by the time I was halfway through a 180 to final. Ran fine on the ground. My first thought was clogged injector, so I removed the line and the injector, checked for contamination. Found nothing. Reassembled, test flew, everything seemed fine.
A few hours of flight time later the problem reappeared, #2 cylinder again, once again it was only after I'd been flying for at least 15 minutes. Warm day, probably 80 degrees at altitude, but not scorching hot. That time it was intermittently less severe, but the cylinder eventually dropped off. During a beeline back to the airport it once again cured itself. Maddening, the worst type of problem to troubleshoot. This time I removed all the injectors, and, after calling Precision Airmotive, disassembled the flow divider to check for contamination. Found nothing. Ran fuel through the system with nozzles in glass jars which confirmed even flow. Swapped injector nozzles between #2 & #4 just in case, to rule that out. Reassembled, test-flew, everything was fine.
Yesterday, 35 hours after the last incident, the problem reappeared, intermittent in the air as always. Once again I returned to the airport and landed, only this time the problem continued intermittently on the ground. I ran it up to about 1500 rpm and watched the engine monitor. #2 would intermittently cut out (every few seconds) and when it did the EGT would drop precipitously. Once again I disassembled the fuel system from the flow divider on, but once again found nothing. I buttoned it up and test-ran it last night but didn't fly- it started and ran fine, all temps came up evenly.
Now I'm thinking about morning sickness, but I'm not sure what the symptoms are. It never happens at first start or when the engine is cold, but maybe that doesn't matter. What would one expect to see on an engine monitor? For what it's worth, I've checked compression, it's consistently 80/77 all around with a warm engine. Checked plugs, they looked fine everywhere yesterday. If an exhaust valve is sticking open, wouldn't EGTs go up instead of down?
I've spoken to a few local mechanics, but they don't have any ideas. I'm new to aircraft engines, but I've been working on ground-based engines my entire life, so I'm comfortable turning wrenches. I've read the description of the "rope trick" and I'm happy to do that if it makes sense.
Thanks in advance for any input!