Mystery EGT excursion

Rupester · #1 03-08-2013, 01:36 PM

Took off today with everything looking fine ... All numbers in the green. Got to about 2500' climbing for 3500' when I got an engine alarm .... "EGT spread too wide". looked at the EGTs quickly and saw that all were 1100 to 1200 except #3 which showed 1470 and still climbing. Yikes ... Never had an EGT go wacky like that. I called for landing and soon after pulling the power back, all EGTs were around 1150. I landed with everything looking oK.... Taxied to the penalty box and did another runup .... Everything normal. Mag/plug check was fine. Took off again and had no problem whatsoever. Flew for 1.9 doing flight testing stuff. No issues. Anyone have an idea ? (BTW, 32.4 hr Hobbs when I took off the first time. )

Kahuna · #2 03-08-2013, 02:00 PM

Best guess would be a plug off line from a # of different reasons. Could have been nothing more than a fouled plug that cleared itself. Could be other ignition related.
Would have been good to do a mag check while the egt was spiked. Dont get nervous when an egt spikes. Take a moment to troubleshoot from a safe spot overhead.

Pmerems · #3 03-08-2013, 03:13 PM

if you see this behavior again and its spikes up closer to 2000 degrees, suspect a loose connection particularly at the crimp connection.

RV10inOz · #4 03-08-2013, 03:30 PM

A mag check would have been a good idea. As mentioned above these can easily be identified by doing that under power, the one failing will show up with dropping egt while others rise, and a bit of rough running.

It is important to note that a faulty plug will fail under load in the engine yet pass the traditional bomb tester.

As a guess the bottom plug on that cylinder may have lead ball buildup.

Rupester · #5 03-08-2013, 06:06 PM

... I'll pull the plugs next week. This weekend is the HopsnProps gig in Oshkosh ... I'll be there until late Sunday. (FYI .. not taking 385TE, for lack of 40 hrs)