Erratic Engine Idle
06-01-2005 | 10:08 PM
#1
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Senior Member
Erratic Engine Idle
Hey guys,
I'm having issues with my engine. I have a thunder tiger .46 mounted inverted on my PC9. For the first couple weeks it ran great. Now its acting up. The idle is REALLY irractic. I have to keep it at a high idle (high enough where the plane moves on grass) to keep the engine running. When its idling, the RPMs go up and down. When throttling up, it runs good once the fuel is cleared out. The problem is I have to idle is soo high so I dont dead stick which causes problems because of fast landings.
I've tried what the manual said about adjusting the mixture. It stated if I pinch the fuel line to the carb and the engine revs up and then dies, it needs adjusted. Well, I adjusted it so when you pinch or disconnect the line, the engine dies (which I am assuming thats what it needs to do). I did notice the head and exhaust seem VERY VERY hot too touch.
I did the obvious like change the glow plug, check fuel lines, etc...
What to do? Is there a FAQ some where that goes in depth on adjusting 2 strokes??
Also, running an engine inverted, is there an advantage to running a short glow plug as opposed to a standard length?
Thanks!!
I'm having issues with my engine. I have a thunder tiger .46 mounted inverted on my PC9. For the first couple weeks it ran great. Now its acting up. The idle is REALLY irractic. I have to keep it at a high idle (high enough where the plane moves on grass) to keep the engine running. When its idling, the RPMs go up and down. When throttling up, it runs good once the fuel is cleared out. The problem is I have to idle is soo high so I dont dead stick which causes problems because of fast landings.
I've tried what the manual said about adjusting the mixture. It stated if I pinch the fuel line to the carb and the engine revs up and then dies, it needs adjusted. Well, I adjusted it so when you pinch or disconnect the line, the engine dies (which I am assuming thats what it needs to do). I did notice the head and exhaust seem VERY VERY hot too touch.
I did the obvious like change the glow plug, check fuel lines, etc...
What to do? Is there a FAQ some where that goes in depth on adjusting 2 strokes??
Also, running an engine inverted, is there an advantage to running a short glow plug as opposed to a standard length?
Thanks!!
06-01-2005 | 11:03 PM
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From: Madison,
AL
RE: Erratic Engine Idle
Sounds like your idle mixture is hosed. I'm not familiar with the TT engine so someone correct me if I'm wrong. Find the idle screw (usually opposite the carb from the main needle valve). I'd run it at the lowest throttle setting you can keep it running at and turn the idle mixture screw until it smooths out. Just like the needle valve, clockwise is lean, counter is rich. I wouldn't have a guess as to where you're at now so try one direction and go the other way if it gets worse.
Cary
Cary
06-01-2005 | 11:06 PM
#3
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RE: Erratic Engine Idle
ORIGINAL: jcmccorm
Sounds like your idle mixture is hosed. I'm not familiar with the TT engine so someone correct me if I'm wrong. Find the idle screw (usually opposite the carb from the main needle valve). I'd run it at the lowest throttle setting you can keep it running at and turn the idle mixture screw until it smooths out. Just like the needle valve, clockwise is lean, counter is rich. I wouldn't have a guess as to where you're at now so try one direction and go the other way if it gets worse.
Cary
Sounds like your idle mixture is hosed. I'm not familiar with the TT engine so someone correct me if I'm wrong. Find the idle screw (usually opposite the carb from the main needle valve). I'd run it at the lowest throttle setting you can keep it running at and turn the idle mixture screw until it smooths out. Just like the needle valve, clockwise is lean, counter is rich. I wouldn't have a guess as to where you're at now so try one direction and go the other way if it gets worse.
Cary
06-01-2005 | 11:33 PM
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From: Partridge, KS
RE: Erratic Engine Idle
For adjusting low end, I adjust it according to transition. Try moving the stick from idle to half throttle quickly and see what happens. After the engine has been run up and cleared out that is. If it immediately dies, you're probably too lean. If it blurbles a bit, it loaded up and is too rich. I adjust mine so that I can idle it for about 25 seconds and have a good transition. low speed needle controls from idle to 1/2 throttle, and high speed from 1/2 to full throttle.
From what it sounds like, you're rich on the low end. Here's why I think what I do. You mentioned that throttling up it's fine once it clears out. If it's rich on low end, it will load up when idling, and when you throttle up, there's too much fuel in the cylinder. Also, if it's too rich when idling, it will load up, and once it gets enough fuel in there, it will extinguish the glow plug. Try running it with the glow ignitor on after the engine has been run up and see if you can idle it any lower. If you can, you're probably too rich. Also, if the RPMs drop when you remove the glow ignitor, that's another sign that you're rich. But, like jcmccorm said, we can't really tell which way your engine is right now, so just experiment a bit, but no more than 1/8 turn at a time on the low end needle. A little goes a long way.
From what it sounds like, you're rich on the low end. Here's why I think what I do. You mentioned that throttling up it's fine once it clears out. If it's rich on low end, it will load up when idling, and when you throttle up, there's too much fuel in the cylinder. Also, if it's too rich when idling, it will load up, and once it gets enough fuel in there, it will extinguish the glow plug. Try running it with the glow ignitor on after the engine has been run up and see if you can idle it any lower. If you can, you're probably too rich. Also, if the RPMs drop when you remove the glow ignitor, that's another sign that you're rich. But, like jcmccorm said, we can't really tell which way your engine is right now, so just experiment a bit, but no more than 1/8 turn at a time on the low end needle. A little goes a long way.
06-01-2005 | 11:50 PM
#5
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Senior Member
RE: Erratic Engine Idle
ORIGINAL: Grant-KS
For adjusting low end, I adjust it according to transition. Try moving the stick from idle to half throttle quickly and see what happens. After the engine has been run up and cleared out that is. If it immediately dies, you're probably too lean. If it blurbles a bit, it loaded up and is too rich. I adjust mine so that I can idle it for about 25 seconds and have a good transition. low speed needle controls from idle to 1/2 throttle, and high speed from 1/2 to full throttle.
From what it sounds like, you're rich on the low end. Here's why I think what I do. You mentioned that throttling up it's fine once it clears out. If it's rich on low end, it will load up when idling, and when you throttle up, there's too much fuel in the cylinder. Also, if it's too rich when idling, it will load up, and once it gets enough fuel in there, it will extinguish the glow plug. Try running it with the glow ignitor on after the engine has been run up and see if you can idle it any lower. If you can, you're probably too rich. Also, if the RPMs drop when you remove the glow ignitor, that's another sign that you're rich. But, like jcmccorm said, we can't really tell which way your engine is right now, so just experiment a bit, but no more than 1/8 turn at a time on the low end needle. A little goes a long way.
For adjusting low end, I adjust it according to transition. Try moving the stick from idle to half throttle quickly and see what happens. After the engine has been run up and cleared out that is. If it immediately dies, you're probably too lean. If it blurbles a bit, it loaded up and is too rich. I adjust mine so that I can idle it for about 25 seconds and have a good transition. low speed needle controls from idle to 1/2 throttle, and high speed from 1/2 to full throttle.
From what it sounds like, you're rich on the low end. Here's why I think what I do. You mentioned that throttling up it's fine once it clears out. If it's rich on low end, it will load up when idling, and when you throttle up, there's too much fuel in the cylinder. Also, if it's too rich when idling, it will load up, and once it gets enough fuel in there, it will extinguish the glow plug. Try running it with the glow ignitor on after the engine has been run up and see if you can idle it any lower. If you can, you're probably too rich. Also, if the RPMs drop when you remove the glow ignitor, that's another sign that you're rich. But, like jcmccorm said, we can't really tell which way your engine is right now, so just experiment a bit, but no more than 1/8 turn at a time on the low end needle. A little goes a long way.
I'll lean it out tomorrow and see what happens.
Someone at the field told me that the high end needs to be adjusted before the low end. Is this true? To me that doesnt make sense.. If the low end runs like crap, it may not even transition into the high end before dying..
06-02-2005 | 06:17 AM
#6
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RE: Erratic Engine Idle
ORIGINAL: bobbykokinos
Someone at the field told me that the high end needs to be adjusted before the low end. Is this true? To me that doesnt make sense.. If the low end runs like crap, it may not even transition into the high end before dying..
Someone at the field told me that the high end needs to be adjusted before the low end. Is this true? To me that doesnt make sense.. If the low end runs like crap, it may not even transition into the high end before dying..
06-02-2005 | 01:01 PM
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From: Batavia,
IL
RE: Erratic Engine Idle
How old is the fuel? I had a similar problem where nothing my friends and I tried worked, and we then realized the fuel was really old. I changed to new fuel and it solved the problem. I feel like an idiot, but at least I learned.
06-02-2005 | 01:12 PM
#8
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RE: Erratic Engine Idle
ORIGINAL: jwalsh1
How old is the fuel? I had a similar problem where nothing my friends and I tried worked, and we then realized the fuel was really old. I changed to new fuel and it solved the problem. I feel like an idiot, but at least I learned.
How old is the fuel? I had a similar problem where nothing my friends and I tried worked, and we then realized the fuel was really old. I changed to new fuel and it solved the problem. I feel like an idiot, but at least I learned.
06-02-2005 | 01:51 PM
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From: hingham, MA
RE: Erratic Engine Idle
the best advice I can give you is to tighten all the screws until they touch then back them out to the factory starting defaults before you adjust anything so that all adjustments are at least close.
06-02-2005 | 02:43 PM
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From: Paso Robles,
CA
RE: Erratic Engine Idle
Bobby,
Replace the glow plug at the first sign of trouble at idle. Ofcourse, you'll have to retune the carb, but if it ran well in the past, then you had trouble, its the glow plug.
3wire
Replace the glow plug at the first sign of trouble at idle. Ofcourse, you'll have to retune the carb, but if it ran well in the past, then you had trouble, its the glow plug.
3wire
06-02-2005 | 08:21 PM
#12
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Senior Member
RE: Erratic Engine Idle
ORIGINAL: rlipsett
the best advice I can give you is to tighten all the screws until they touch then back them out to the factory starting defaults before you adjust anything so that all adjustments are at least close.
the best advice I can give you is to tighten all the screws until they touch then back them out to the factory starting defaults before you adjust anything so that all adjustments are at least close.
Replace the glow plug at the first sign of trouble at idle. Ofcourse, you'll have to retune the carb, but if it ran well in the past, then you had trouble, its the glow plug.
It is possible that you have an air leak also. Check the fuel lines for cuts.
