I experienced an engine failure while leveling off at FL220 this afternoon. I have almost 200 hours over 15 months on this 2007 IV-P with the TSIO-550B engine, which has 450TT and 220 STOH. We had been tweaking the baffles and checking the CHT probes by swapping probes 5 with 3 and 2 with 4. We had just seen a great improvement in CHTs with the modifications. I was in the process of climbing to FL220 to get some cruise data at 75, 65, and 55 %. Because of the typical ISA+25 Gulf Coast afternoon temps, I had to level off at 12 and 18 for about 4-5 minutes to let the oil temp cool off. The climb temps looked good passing 200 and 210 to continue to 220. When I reached 220 and began the level off, immediately I noticed a very sudden rise in CHTs and EGTs from about 400 where I had expeced them to peak in the climb. 6 + 8 elashing red temps will get your attention right away. (I have the early warnings set at 420 and 1700). The temps came rapidly up to just
 below red line in the high 430s. I have not seen this pattern before in 200 hours in this airplane and with many hot day climbs to the FL200s. I began to slowly reduce throttle, trying to guess whether it was better to keep cooling fuel flow and high power or throttle back to counter the rising temps.
 As I pulled the throttle back, I was able to arrrest the rise but soon noticed the EGTs rapidly dropping. At this point there was no response to throttle inputs. I notified center of my descent, to which he replied that I should ask for a descent clearance first. I replied that I was aware of that procedure, but believed I had a powerplant failure and did not have an option. I turned toward PSX, the nearest long piece of concrete and pulled the prop back for max glide. The engine windmills nicely at max glide of 120KIAS( I have wondered if it might stop the windmill at 120, best L/D and then loss of oil pressure would send the prop back to flat pitch). I got out the engine fail/airstart checklist and switched from the left to the right tank. I notified center of my intention to airstart. Passing 17K, I recall telling him I had about 17 minutes and could easily make the airport at 17 miles. Shortly thereafter at 16500 the engine responded to throttle
 inputs, but initially roughly like a cold start. Slowly allowing the engine to rewarm, I got normal power back. Satisfied with the recovery and airstart, I turned back to homebase about 35 milees away and shot a precautionary approach to high key at Houston Southwest.
 Our best guess after review with my mechanic and a conversation with Tim Wilson at Lancair was that the culprit was temporary fuel starvation. I am guessing that the sudden rise in the EGTs and CHTs was the result of an uncommanded leaning of the mixture as the fuel supply dropped. I did not catch a good record of the fuel flow until after the successful recovery. From then on it was normal. The tanks both had been filled before  the previous flight and only about ten gals had been used from both tanks, so there was about 42 gal. in each. Preflights indicated no obstruction to the wingtip vents and this was true postflight. Fuel samples are done first flight of each day and this was the third flight today. The low boost was on passing 10,000 in the climb in accordance with the checklist. I did not get around to trying the high boost because the failure appeared to clear by switching tanks. when I reached a safe glide range, I tried switching back to the
 left tank and saw no change in fuel flow. I suspect a fuel vent blockage at the freezing level, but I had not flown through any visible moisture this afternoon. Tops of the towering CU was about 10K widely scattered, so they were easy to dodge and avoid moisture and ice in the climb. The engine behaved perfectly thereafter and responded well to clearing procedures during the precautionary approach.

1. Anybody see this pattern before?
2. Any suggestions on troubleshooting or where to look for the cause?
3. What would you check prior to continuing operations other than a thorough engine inspection and fuel system check?

Thanks for the good information and guidance on the LML,
Bill Miller
USN Test Pilot
L-IVP, 191 hours