backfires and misses when i'm accelerating
Thread Starter
|
Freshman User
Joined: Mar 2005
Posts: 45
Likes: 0
From: near sacramento
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
Elder User
Joined: Nov 2004
Posts: 517
Likes: 0
My truck did the same thing and it was a clogged up jet in the carb. It may be time to open her up and do a lite rebuild. Mine would idle and rev fine in the driveway but as soon as i took it out it would buck and stave for fuel.
Senior User
Joined: Jun 2003
Posts: 286
Likes: 1
From: Ousley, GA
I would check for vacuum leaks first. Easy to do and takes very little time. Just spray or use an unlit propane torch around your fittings and mounts. If you get a change in idle at any of your locations you have found where it's sucking air.
Elder User
Joined: Jan 2004
Posts: 561
Likes: 0
From: houston
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.
Thread Starter
|
Freshman User
Joined: Mar 2005
Posts: 45
Likes: 0
From: near sacramento
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?
Elder User
Joined: Jan 2004
Posts: 561
Likes: 0
From: houston
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.
Trending Topics
Junior User
Joined: Feb 2005
Posts: 74
Likes: 0
From: Kokomo, IN
had a backfire through the carb one time, found a idle adjustment screw almost all the way in, and the other one out to correct setting. Also the cough sputter problem sounds like an accelerator pump to me as well..
Good Luck
Good Luck
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
AEV FXL Super Duty - the Super Duty Raptor Ford Doesn't Make
Brett Foote
Lobo Vs Lobo: Proof the F-150 Lobo Should Be Even Lower!
Michael S. Palmer
Ford's 2001 Explorer Sportsman Concept Looks For a New Home
Verdad Gallardo
10 Best Ford Truck Engines We Miss the Most!
Joe Kucinski
2026 Shelby F-150 Off-Road: Better Than a Raptor R?
Brett Foote
2027 Super Duty Carhartt Package First Look: 12 Things You NEED to Know!
Michael S. Palmer
Junior User
Joined: Aug 2004
Posts: 59
Likes: 0
--- Just a thought, fire it up in the dark, and see if you have any plug insulation that has gone bad.. I just had that problem, after changing the same parts you did, and it turned out that I had a cracked insulator on plug no 2.
Have a gooder!!
JA
Have a gooder!!
JA
Elder User
Joined: Nov 2004
Posts: 517
Likes: 0
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; Oct 11, 2005 at 06:21 PM.
Thread
Thread Starter
Forum
Replies
Last Post
ColtonMullis
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
2
Jan 20, 2014 03:53 PM
areoseek
1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks
26
Sep 25, 2013 05:30 PM
kadrocker
1973 - 1979 F-100 & Larger F-Series Trucks
15
Dec 18, 2009 07:45 PM