I am new to the sport. Only about 4 months of flying e every few weekends. Enjoyed it so far until my engine problems. Started with a hanger 9 p-51 pts. Great plane. I had engine problems and changing a glow plug and it seemed to fix it. Only had about a gallon of fuel through the thing. I got a second plane hanger 9 arrow 40. Fly's great. I got the basic and put my own flight pack and engine in it. A thunder tiger 42 that my brother got about 4 years ago and only ran a few tanks through it. It has set in his garage until now. I put it on my plane started it up and it ran great with no adjustment over a dozen flights. Now about 10 tanks into it I flew it last weekend for one flight brought it in, fueled it for the next run and then the problem started. I am having the same problem as my p-51 except that changing the glow plug does not fix it. Put a brand new one in it and was doing the exact same thing. Will run fine with glow plug starter but as soon as I remove the starter it dies. Sometimes after I remove the starter it will continue to run at mid or full power but only for maybe 10 seconds, but it does not sputter, just an abrupt stop. It has smoke coming out of the exhaust and at full power with the starter on it I turn the needle rich until it bogs down a little and back it back a turn or 2 until it starts running good. Am I doing something wrong? Can it be a fuel problem as far as fuel going bad? Is the engine loosing compression? Are glow plugs that damn sensitive? Any help will be greatly appreciated. I thought about taking it to the rc shop and let them try to fix it but would like to figure this out myself and hopefully make this a cheap fix. The only thing I can think of is to try another new plug, but I have already tried another used plug as well as the new one and did the same thing, so not sure that another new plug is the fix. Hard to believe an engine this small is this big of a pain. Thanks!