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We just recently completed the annual on my ASII. Before the inspection, it ran fine. I'm running a stock O360 with a PS5C pressure carb and a 4 into 1 exhaust. Logic would seem to say that we did something to cause this problem during the annual inspection.
During the first flight after the inspection, all started out well. I was making a few laps around the field and did a touch and go. During the climb out after the touch n go, after a minute or so of WOT operation, the engine started to run rough. Reducing power smoothed it out. Carb heat also smoothed it out. During another flight later that day, all went well. Climb out was fine and I made a few laps around the field at leaned out cruise power without any problems. Then, I went to full power and all was fine for a minute or two, then it started running rough again. Once again, reducing power or carb heat solved the problem. Fuel pressure was normal during the rough engine operation. I also noticed that it didn't take nearly as much movement of the mixture control to get it the egt to where i cruise at
My conclusion after this was that the mixture was too lean at WOT and carb heat richened it enough to cure the problem. So, I checked the tank vents, sumped the tanks, checked the intake tube connections, made sure that the mixture control was working properly, and checked the fuel filter in the carb. All checked out fine. A static RPM check yielded 2350 RPM which is whats its been for a few years.
Just to test my too lean theory, I adjusted the main discharge nozzle one click richer. I could not replicate the problem on the ground. So, I decided to fly it again. All went well for quite a while. If I try leaning at WOT, I get 100-150 degrees of EGT rise before the engine starts to run rough which should be fine. But, after artificially leaning the mixture too much at WOT, the engine wouldn't smooth out when I went back to full rich. The EGT temp went back down, but it was still running rough. I did a mag check and it ran rough on both. Carb heat again corrected the problem. After that, I switched the carb heat off and went back to WOT and it ran fine. I also noticed during this flight that the EGT goes up as I reduce the power setting from WOT to 75% by 150-200 degrees or so. It may have always done this, but it did seem weird.
At any rate, I don't know what to do next. I really think that we did something to cause this during the annual inspection. Here is a pertinent list of what we touched during the annual.
1. Removed, cleaned, and gapped spark plugs.
2. Checked mag timing. It was spot on so we didn't adjust it.
3. Removed fuel pump to facilitate the replacement of the battery.
4. Replaced fuel filter in wobble pump.
5. There was only about 3 or 4 gallons of fuel in the tank during the inspection so I did have to add about 15 gallons before I test flew the airplane.
6. Replaced the engine mounts.
7. Replaced all of the battery cables
8. Did a compression test and scoped the cylinders, all looked fine.
Any ideas on where to go next?
During the first flight after the inspection, all started out well. I was making a few laps around the field and did a touch and go. During the climb out after the touch n go, after a minute or so of WOT operation, the engine started to run rough. Reducing power smoothed it out. Carb heat also smoothed it out. During another flight later that day, all went well. Climb out was fine and I made a few laps around the field at leaned out cruise power without any problems. Then, I went to full power and all was fine for a minute or two, then it started running rough again. Once again, reducing power or carb heat solved the problem. Fuel pressure was normal during the rough engine operation. I also noticed that it didn't take nearly as much movement of the mixture control to get it the egt to where i cruise at
My conclusion after this was that the mixture was too lean at WOT and carb heat richened it enough to cure the problem. So, I checked the tank vents, sumped the tanks, checked the intake tube connections, made sure that the mixture control was working properly, and checked the fuel filter in the carb. All checked out fine. A static RPM check yielded 2350 RPM which is whats its been for a few years.
Just to test my too lean theory, I adjusted the main discharge nozzle one click richer. I could not replicate the problem on the ground. So, I decided to fly it again. All went well for quite a while. If I try leaning at WOT, I get 100-150 degrees of EGT rise before the engine starts to run rough which should be fine. But, after artificially leaning the mixture too much at WOT, the engine wouldn't smooth out when I went back to full rich. The EGT temp went back down, but it was still running rough. I did a mag check and it ran rough on both. Carb heat again corrected the problem. After that, I switched the carb heat off and went back to WOT and it ran fine. I also noticed during this flight that the EGT goes up as I reduce the power setting from WOT to 75% by 150-200 degrees or so. It may have always done this, but it did seem weird.
At any rate, I don't know what to do next. I really think that we did something to cause this during the annual inspection. Here is a pertinent list of what we touched during the annual.
1. Removed, cleaned, and gapped spark plugs.
2. Checked mag timing. It was spot on so we didn't adjust it.
3. Removed fuel pump to facilitate the replacement of the battery.
4. Replaced fuel filter in wobble pump.
5. There was only about 3 or 4 gallons of fuel in the tank during the inspection so I did have to add about 15 gallons before I test flew the airplane.
6. Replaced the engine mounts.
7. Replaced all of the battery cables
8. Did a compression test and scoped the cylinders, all looked fine.
Any ideas on where to go next?
