I have flown 17 uneventful hours behind my Barrett IO-390X. It has run perfectly until today. On climb out I noticed the engine loose power or stumble, slightly and briefly, three times and I immediately turned back to land. This has not happened before.
Yesterday the wx was a bit snotty so I de-cowled and looked for any anomalies - none were found. This mornings temperatures were downright awesome at 80. This engine never runs hot, cylinders always below 330 and it's hard to get oil temps above 190. DA was about 2000 ft this morning and field alt is 600.
I pulled the chip from the G3X and pasted today's flight on savvy. The attachment is a snapshot from run-up (prop cycled 3 times), short taxi to runway and the very short flight to landing. Notice EGT's on 1,2 are divergent from 3,4.
I pulled all the fuel injectors and checked for blockage - nothing found. I have dual PMags and each PMag powers one spark plug per cylinder - eg cylinder 1 has a plug powered by the Left PMag and a plug powered by the Right PMag, same for all cylinders. I have not checked the timing yet.
This takeoff was done with fuel pump on throughout the short flight. As I was climbing out I started reducing rpm from 2700 to 2500 when I started to feel the slight power loss.
Later today I did a PMag ground check again and both were functioning properly on the ground but I did notice that it would not idle unless the mixture was pulled way way back. Boost pump was not on. I de-cowled again and found that the mixture control is moving correctly stop-to-stop.
After every flight I post my flight to savvy. Up til today the EGT's on all cylinders have been in sync and look very normal.
Looking for suggestions on what to look for next.