Chris Engler
Active Member
For those of you that have been following my "XP-400 Still Coughing" thread, I'm delighted to report I had to start a new thread with a different name since the problem has been identified.
After spending 2 months and changing out fuel servos, mags, exhaust, checking plugs, spider, injectors, confirming fuel flow and pressure, etc. etc., and not finding anything, I spent today at the airport, pulled the engine off the airplane, removed the accessory case and there it was....the cam to crank gear train was "one tooth off".
The engine would start and run fine till 2500 RPM then stumble and sputter rich. Leaning would clean up the coughing and allow 2600 RPM static. Many (including the mechanic on our filed) felt the engine would run rough throughout the entire RPM range with the cam timing off but Birddog from this forum insisted I check as he experienced similar symptoms with an engine with the same issue. BIG high five to Birddog for his persistence in having me check!
Now at least we've got the problem identified and can work on the solution....will be chatting with Superior first thing Monday morning.
Thanks to all those that provided experence, insight, and encouragement as I worked through a frustrating couple of months!