acceleration problem
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Freshman User
Joined: Mar 2017
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acceleration problem
hey all, i have a 1972 f250 360. when i step on the gas it sputters. But when i just apply it as normal it does not. and when i am at around 70 mph it does it even when i am not stepping on it. It idles fine and accelerates fine if i don't stomp on it. What do you all think the problem is?
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
Well since we don't know anything of what or when the last tune up was done.
Check all rubber vacuum lines for leaks.
Start by doing a compression test looking for low cylinders psi.= bad valves/exh. seats
if all above 125Lbs should be good for a tune up like plug wires, points & condensor best to use motorcraft, Dizzy Cap/rotor, Check vacuum advance if good, reset timing.
Orich
Check all rubber vacuum lines for leaks.
Start by doing a compression test looking for low cylinders psi.= bad valves/exh. seats
if all above 125Lbs should be good for a tune up like plug wires, points & condensor best to use motorcraft, Dizzy Cap/rotor, Check vacuum advance if good, reset timing.
Orich
Logistics Pro
Joined: Aug 2015
Posts: 4,093
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From: Lind, WA- Eastern WA
Which type of electronic ignition-DuraSpark, MSD,or is it a points replacement kit? Also what is the timing set at?
Posting Guru
Joined: Apr 2006
Posts: 1,477
Likes: 7
From: NAMPA, ID.
Probably need to treat it with Amsoil, Seafoam, Marvels Mystery oil, change the coolant to Water Wetter, add a K&N air filter, add a Pertronix ignition system with MSD, Accel Super Coil, Iridium spark plugs, and two 850 double pumpers with a "3/4" cam. That should do it.
Lead Driver
Joined: Aug 2003
Posts: 7,592
Likes: 10
From: **** hole San Jose ca.
Probably need to treat it with Amsoil, Seafoam, Marvels Mystery oil, change the coolant to Water Wetter, add a K&N air filter, add a Pertronix ignition system with MSD, Accel Super Coil, Iridium spark plugs, and two 850 double pumpers with a "3/4" cam. That should do it.
All good useless information to help this guys problem!
Orich
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I am not sure if it is duraspark, i see no markings to indicate. i am not sure about timing but i will check when i check my compression today.
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Ford Parts Specialist
Joined: Nov 2006
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From: Simi Valley, CA
1974/85: Squarish shaped module located on left fender inner apron, just in front of the firewall.
Above where the wires feed out, is a colored plastic grommet used to ID it. Blue grommet is the most common, but it could also be black, brown, red or yellow.
Genuine Motorcraft module will be so marked and will have ID engineering numbers cast onto it.
Inside the dizzy is a stator aka magnetic pickup coil.
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Freshman User
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yes it has the module and the stator inside. i checked the compression and it is 125 psi on all cylinders. while doing so i think i found the problem, the number 5 cylinder spark plug was loose and the number 6 cylinder spark plug wire boot was not seated on the electrode. tomorrow when i take it for a drive i should know. if it is still doing it i will check timing. I did notice the the pugs looked like they are running hot, whitish grayish on the electrode and light brown on the porcelain of the inside electrode. The pugs were gaped at .030. I remember something about they should be .034, is this true? I can most certainly tell you all, i am having a lot of fun working on and learning all bout my truck.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Plug gap isn't TOO critical, from your numbers. .030" to .035" for a point and condenser system is OK. Check to see if they are the right number and and heat range for your engine. The stock OEM spark plug # is fine for 99% of folks.
Carburetors need to be gone through every several years at least. They get filled with varnish and sludge, rust and sediment because the fuel breaks down, most of these trucks don't get driven very much anymore. Old, varnished fuel in the tank and lines, plugs filters and screws up carburetors, stuck lifters.
Focus on one area at a time. Ignition first, then carburetion maybe. You want the shop manual for your truck. Will save a lot of aggravation and you'll learn a lot about diagnostics and troubleshooting.
Carburetors need to be gone through every several years at least. They get filled with varnish and sludge, rust and sediment because the fuel breaks down, most of these trucks don't get driven very much anymore. Old, varnished fuel in the tank and lines, plugs filters and screws up carburetors, stuck lifters.
Focus on one area at a time. Ignition first, then carburetion maybe. You want the shop manual for your truck. Will save a lot of aggravation and you'll learn a lot about diagnostics and troubleshooting.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
.035", not .35". Plug gaps can be widened with electronic ignition, but not that much.
Hesitation and stumbling, a good bet is to check the accelerator pump circuit of the carburetor. With the engine OFF, look for two streams of fuel squirting when the carburetor is goosed while looking down the carb throat.
With old trucks it just pays to pull the carb and go through everything, there's a 99% chance it's all buggered up and has been "tuned" by a previous owner with the Golden Screwdriver. Get the carb manual to download online and start from the beginning, make sure fuel pump output is adequate and fuel height in the bowl is correct, etc.
Hesitation and stumbling, a good bet is to check the accelerator pump circuit of the carburetor. With the engine OFF, look for two streams of fuel squirting when the carburetor is goosed while looking down the carb throat.
With old trucks it just pays to pull the carb and go through everything, there's a 99% chance it's all buggered up and has been "tuned" by a previous owner with the Golden Screwdriver. Get the carb manual to download online and start from the beginning, make sure fuel pump output is adequate and fuel height in the bowl is correct, etc.
Cargo Master
Joined: May 2015
Posts: 2,350
Likes: 7
From: Garland, Tx
I'm running pertronix and flamethrower coil and gaps is at .40-.43.
Do NOT look down the throats of the garb while it is running. If that thing pops thru the carb, you'll have bigger headaches than a stumble. Use a mirror
2X on the carb rebuild. What carb is on it?
Do NOT look down the throats of the garb while it is running. If that thing pops thru the carb, you'll have bigger headaches than a stumble. Use a mirror
2X on the carb rebuild. What carb is on it?