backfires and misses when i'm accelerating
#1
backfires and misses when i'm accelerating
ok, i thought i had her running like a champ... but... whenever i try to accelerate it stalls out and backfires?!
heres the specs on my truck
74 f250
360, 4bbl, new plugs/wires/coil/cap/rotor....
4x4
auto trans
it's seems kinda weird cause it idls great and if i stop on it, it sounds smooth but takes a long time to get up to speed. crusin on the freeway is kinda rough too. i'm loosing serious power to this problem and i've checked the whole ignition system a dozen times. any ideas? carb stuff maybe? i havn't messed with it and it worked before so it doesn't seem like that would be it. it is my driver so it's kinda embarasing putting around town in a big old monster truck. thanks to anyone who can help
heres the specs on my truck
74 f250
360, 4bbl, new plugs/wires/coil/cap/rotor....
4x4
auto trans
it's seems kinda weird cause it idls great and if i stop on it, it sounds smooth but takes a long time to get up to speed. crusin on the freeway is kinda rough too. i'm loosing serious power to this problem and i've checked the whole ignition system a dozen times. any ideas? carb stuff maybe? i havn't messed with it and it worked before so it doesn't seem like that would be it. it is my driver so it's kinda embarasing putting around town in a big old monster truck. thanks to anyone who can help
#2
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#5
Backfire through the carb means it's too lean. Stumbling while trying to accelerate means your accelerator pump isn't discharging enough fuel. I would increase the stroke on the pump and see if that helps. Also moving up a couple of jet sizes won't hurt anything accept mileage. Carb tuning by the sat of your pants can take some time. Keep checking plug color. You wan a nice chocolate brown color. Good luck.
#6
i'm having a hard time figureing my timing. if i set it where my chiltons says it should be i cant accelerate hardly at all. i have it advanced quite a bit so it runs better, i know thats bad for it.
also my plugs have a white color. i suppose that means it running rich. so either its running rich and getting to much or it's running lean and not getting enough.
one last thing. it's a holley 4 bbl. and i'm not sure where my mix ajustment is. is that just the float ajustment or is there another one somwhere?
also my plugs have a white color. i suppose that means it running rich. so either its running rich and getting to much or it's running lean and not getting enough.
one last thing. it's a holley 4 bbl. and i'm not sure where my mix ajustment is. is that just the float ajustment or is there another one somwhere?
#7
White plugs means you are lean. Holley makes a lot of different carbs. Usually the mixture screws are located on the sides of the mereting block. I would buy a book on Holley carbs. You will gain a world of knowledge from it. Also the mixture screws only control fuel at and just above idle, then the run circuit comes into play. You say it's running fine at idle. As for the timeing, are you sure the advance is working? Does the timeing move when you increase the RPM? Again, check the accelerator pump. You need a good shot of fuel when you tip open the throttle because you loose all your vaccum which draws the fuel. Also double check your float level. Good luck.
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You're staving for fuel hence the no power and white plugs. It could be a partially clogged passage in the carb, or maybe just the fuel filter/pump. I started with the easiest and finally worked my way to the carb and when I opened it it was obvious that the chunk of brown crud sitting in one of the jets was the culprit.
good luck and let us know.
BTW it would also help to know if your problem just started right away or if it's always been like this
good luck and let us know.
BTW it would also help to know if your problem just started right away or if it's always been like this
Last edited by yield2s; 10-11-2005 at 06:21 PM.
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