P-Mag question. Possible misfire?

lostpilot28 · #1 09-26-2010, 05:33 PM

I flew to Reno this weekend and back...nice easy flight. This is the second time I've flown down there. For the most part, the engine runs very smooth. But occasionally the engine will skip a beat. It happens very fast, and it's imperceptable if you're not paying attention.

I don't believe it's either of the P-mags. If I had to guess, I'd think it was the auto spark plugs. They've got 86 hours on them now, and I've never cleaned them or anything.

Anyone have any ideas?

Steve Sampson · #2 09-26-2010, 11:53 PM

Sonny, since auto plugs are so cheap why not put 8 new ones in. If the problem goes away....solved. Clean the old ones, put them on a tester and keep the good ones as spares.

If not, I would take a look at the harness perhaps.

PS It raises a question I have never received a practical answer to. I am a bit leery of taking my auto plugs out to look at them because I can neither replace/anneal the washers. Any practical solutions....anyone?

apkp777 · #3 09-27-2010, 05:49 AM

Curious what you are running for plugs. I just switch from the BR8ES to the BR8EIX Iridiums. Much more $$, but I figured still a whole lot cheaper than aviation plugs.

FWIW I seem to hear every engine I fly behind miss a beat now and then. Since I had a failure on takeoff my ears are always tuned to the sounds of 4 well timed cylinders.

As far as annealing your washers, are you talking about annealing the spark plug washer or the adapter washer? The spark plug washer doesn't need to be annealed and the adapter washers can be annealed easily with a torch and some coolant.

RV8R999 · #4 09-27-2010, 06:31 AM

Tony,

What was the result of the switch to the more expensive plugs? Any change in CHTs? Just curious.

Ken

apkp777 · #5 09-27-2010, 06:37 AM

Quote:

Originally Posted by RV8R999

Tony,

What was the result of the switch to the more expensive plugs? Any change in CHTs? Just curious.

Ken

I installed the plugs and haven't flown on them yet. I hope to fly this morning or tomorrow and will report. I also tested my leads and (180ohms/ft) and they seem to be good.

My cheap plugs were fine. I have had one cyl (#3) that the CHT runs cooler and has a higher EGT and I wanted to eliminate the plugs as a culprit.

Steve Sampson · #6 09-27-2010, 08:41 AM

Quote:

Originally Posted by apkp777

As far as annealing your washers, are you talking about annealing the spark plug washer or the adapter washer? The spark plug washer doesn't need to be annealed and the adapter washers can be annealed easily with a torch and some coolant.

I have been trying to leave the adapters in and just take the auto plugs in/out to reduce the wear & tear on the engine threads. But you have a good point.

apkp777 · #7 09-27-2010, 10:54 AM

I flew today with the BR8EIX Iridium plugs. I would definitely say that the engine ran very smooth. Normally when I approach peak EGT, the engine stumbles uncomfortably. Today I was surprised that it was not nearly as noticeable. Unfortunately however the change did nothing for my Low CHT high EGT problem on #3.

Jkkinz · #8 09-27-2010, 12:00 PM

Steve look at this video, I think it should answer any questions you might have if you are using copper gaskets

http://www.eaavideo.org/video.aspx?v=57437956001

NDrv8r · #9 09-27-2010, 01:01 PM

If this is just an occasional hiccup, consider the possibility of a valve sticking. this will occur on engines closer to tbo.

lostpilot28 · #10 09-27-2010, 01:06 PM

Quote:

Originally Posted by NDrv8r

If this is just an occasional hiccup, consider the possibility of a valve sticking. this will occur on engines closer to tbo.

It is an occasional miss...pretty random, actually. Although at one point yesterday it happened within 10 seconds of each other. I hope it's not a sticking valve...my engine has 86 hours on it since new!