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- Mar 18, 2017
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1965 Cherokee 160C, Lycoming O-320-D2A.
A few months ago, I was headed out the fly and had a big RPM drop on the left mag. After taxiing back and consulting with a mechanic, I went off to a remote part of the field, did a full power run-up with leaning, and the problem seemed to clear. Off we go flying.
The issue has reoccurred a few times, but seemed to clean up if I blew it out. I figured I'd be in for a plug removal and cleaning soon enough. As luck would have it, I went out to fly a few nights ago, and got the same issue. This time, I called off a takeoff (it didn't feel right), and was getting that big RPM drop on the left mag when I taxied back to diagnose.
Consult the mechanic again, and we ageeed to pull and clean plugs. Upon testing, I found that I had a hodgepodge of plugs installed (different manufacturers, different heat ranges), and a number didn't test well. 8 new REM 38Es later, back in business.
When I went out yesterday, I was hit with the same issue on the full mixture runup. I know plugs could not have fouled that quickly, so I played with the mixture a bit at a full power run up. Sure enough, I could watch the RPMs get unhappy at full rich, but find their happy spot when I leaned out. I'm in Arizona, which is presently the surface of the sun. It was hot out, but not yet over 100.
2 brief and uneventful flight legs later, all appeared reasonably well. So now that I've got 8 new plugs and what appears to be an ongoing intermittent problem, I wanted to poll the electorate for thoughts.
I don't believe it's a fouling issue, as I can't see new plugs loading up that quickly. I lean for taxi and after landing, as well as every chance I get on climb out and at altitude. The mags are Slicks, and appear (externally) to be reasonably young and in good condition. As the issue is intermittent, I wouldn't think bad impulse coupler spring.
A few months ago, I was headed out the fly and had a big RPM drop on the left mag. After taxiing back and consulting with a mechanic, I went off to a remote part of the field, did a full power run-up with leaning, and the problem seemed to clear. Off we go flying.
The issue has reoccurred a few times, but seemed to clean up if I blew it out. I figured I'd be in for a plug removal and cleaning soon enough. As luck would have it, I went out to fly a few nights ago, and got the same issue. This time, I called off a takeoff (it didn't feel right), and was getting that big RPM drop on the left mag when I taxied back to diagnose.
Consult the mechanic again, and we ageeed to pull and clean plugs. Upon testing, I found that I had a hodgepodge of plugs installed (different manufacturers, different heat ranges), and a number didn't test well. 8 new REM 38Es later, back in business.
When I went out yesterday, I was hit with the same issue on the full mixture runup. I know plugs could not have fouled that quickly, so I played with the mixture a bit at a full power run up. Sure enough, I could watch the RPMs get unhappy at full rich, but find their happy spot when I leaned out. I'm in Arizona, which is presently the surface of the sun. It was hot out, but not yet over 100.
2 brief and uneventful flight legs later, all appeared reasonably well. So now that I've got 8 new plugs and what appears to be an ongoing intermittent problem, I wanted to poll the electorate for thoughts.
I don't believe it's a fouling issue, as I can't see new plugs loading up that quickly. I lean for taxi and after landing, as well as every chance I get on climb out and at altitude. The mags are Slicks, and appear (externally) to be reasonably young and in good condition. As the issue is intermittent, I wouldn't think bad impulse coupler spring.
