Thought we fixed our RPM drop

We have a 7A with one Slick mag and impulse coupling and one PMag. About a month or so ago my plane partner was flying and on climb out experienced an RPM drop that while attention getting was short lived. It happened once more and we dropped the data from our Dynon and it showed the RPM drop and associated EGT rise but only on the #1 cylinder. Further digging showed what we thought was arcing at the autoplug to wire connection. We replaced that lead wire.

We had already pulled the carb and had it overhauled as it was time, it was also time for the Slick mag to be rebuilt and had it done as well.

Flying today I visually saw the RPM drop and all EGTs rises for a total of six seconds before all returned to normal. Dropping the Dynon data showed the same.

We are thinking one of our mags is intermittently being grounded.

Any thoughts ?

s24789 said:

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Flying today I visually saw the RPM drop and all EGTs rises for a total of six seconds before all returned to normal. Dropping the Dynon data showed the same.

We are thinking one of our mags is intermittently being grounded.

Any thoughts ?

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I'll bet if you post the engine data on Savvy and provide a link, the guys with the decades of experience will tell you what's wrong. Since it affected all cylinders, the only three common things are the carb, and the two ignitions. Your idea of a possible intermittent ground seems like a good candidate.

When was the last time the PMAG was serviced?

Walt it never has been serviced. I just looked it up and we installed it in 3/5/14 and it has 885 hours.

s24789 said:

Walt it never has been serviced. I just looked it up and we installed it in 3/5/14 and it has 885 hours.

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Send it to Brad for a spa day and install new wires and plugs, that’s what I’d do.
Another likely cause is broken/loose wires on the connector which you will obviously check when you remove it.
(I’ll wager you will find play in the bearings, and loose wires in the ‘connector’).