Went to fly my new plane today with my engine that only has 2 flights and 4 breakin runs on it. The engine a .40 ASP always ran good but after a min of low idle it would develope a little hesitation. There are 2 adjusting screws , high and low. The low is in the throttle barrel behind the prop. Real fun to get to with the engine running. Anyway after repeatedly trying to adjust the idle its still not working right. Today the engine would idle until I remove the glow igniter then it dies after a second. No signs of rough idle or anything and at high rpm it runs fine. Its only the 6th time Ive run this engine. I start with the adjusting screw 1 1/2 turns out and make very small 1/8 turns and wait a few seconds for the change. It will sound just right till I remove the igniter then after a second it suddenly just quits. Tried 1/8th turns up to a total of 1/2 turn both ways but no difference. If I open the throttle about 1/2 way it will run with glow igniter off. The engine was running fine first 10 min till I tried to tweak the idle ( dumb me ) I did the original adjustments without this problem though. Im wondering if its just a bad glowplug. Im useing a fox, long, with idlebar.

While the glow plug may be bad, you need to make sure that your engine is up to temperature and all excess fuel removed before adjustments are made.

do you still have the plug you used to break it in, in the motor? if so, try a new one and see what happens. if that doesnt cure it, it sounds like the low needle is pretty rich. re set that needle to 1 1/4 out to start with and see what happens. also, you shouldnt try to adjust that needle with the engine running,

One thing is any new engine will be a littlw erratic untill it is well brocken in. Just hang in there until you get a few more flights on it and it will likly get better.It sounds to me that you are expecting too much too soon for a new engine.

Ok...here's what your going to do. First thing is...set your low speed needle back to the stock setting if you still knoe it. If not...start about two turns out from closed. Also set the high speed needle about the same...two, or two and a half turns out. Now...start the engine. Open throttle up all the way. Adjust the high speed needle until you reach max rpm. You will most likely have to lean it a bit to get max. This means turn the needle IN one eighth of a turn at a time and wait for the engine to respond with either a slight increase in rpm, or a slight decrease in rpm. If you get to a point where you notice a slight decrease in rpm...then you have passed max rpm and are running in a lean condition, and should turn the needle out just a bit until the rpms increase again. This is in the neighborhood of max rpm...and you can run just slightly on the rich side of this setting to avoid damage to your new engine...but DO NOT run it in what is called a rich "four stroking" condition. NEXT...let it run about a tank, or for about 5 min. with it at this setting with the wide open throttle. Kill the engine and let it cool off. REPEAT! Start the engine again...adjust needle for top rpm and run another tank through...at wide open throttle. Kill the engine and let it cool down again.

OK...at this point you can focus on the low speed needle...the idle and transition. Start the engine and adjust for max rpm as before. After you are satisfied, let the engine idle for a bit and then open the throttle to wide open setting smoothly, and without hesitation. LISTEN...does the engine gurgle and sputter...if so it's too rich. If it dies immediately...then it is to lean. If it transitions with a bit of hesitation, and seems to fall off...then you are still too lean, but getting close. Turn the low speed needle IN to lean the engine and OUT to richen it. One eighth turn at a time, and then restart the engine, and check the idle and transition again until you get it.

CHECK your settings by using the pinch test. While the engine is running wide open...pinch the fuel line just behind the fuel inlet nipple...and LISTEN...does the motor increase in rpm a lot...if so you are still too rich...if it sags, you are too lean. IF it increases very little in rpm, but does not sag or fall off...then you are there. You may also hold the plane in a nose up attitude, and LISTEN for the same clues.

THIS ASSUMES THAT YOUR ENGINE/TANK INSTALLATION IS GOLDEN! No air leaks, tank-engine relation, etc.

Hope this helps.