BACKFIRE! BACKFIRE! BACKFIRE!
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New User
Joined: Nov 2012
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From: Gaithersburg, MD
BACKFIRE! BACKFIRE! BACKFIRE!
Hey all. Hope everyone is enjoying their weekend thus far. I know I am. Especially when the Redskins win tomorrow. lol
Anyways, I have a:
1988 Ford Bronco FS
5.8 351W
The truck is just about as stock as can be so far.
So I bought this truck about a year and a half ago. It sat a whole year and now I am having problems... of course.
Today I did a tune up:
Spark Plugs, Wires, Distributor cap, Rotor, ignition coil and fuel filter.
EDIT! After a few seconds of holding the pedal, all runs GREAT! like nothing wrong. Only sluggish when I initially push on the throttle....
Prior to the work I did, when I would slam on the gas, it would be very sluggish and then back fire through the intake. If i dont press the pedal hard, its sluggish but doesnt back fire.
Well after all the work done today, ITS STILL DOING THE SAME THING!
So any idead guys?
Thanks
Bobby
Fleet Mechanic
Joined: Sep 2003
Posts: 1,716
Likes: 15
Sounds like it is running very lean.
A Fuel delivery problem, check fuel pressures.
OR
a tip-in throttle lean problem. Carb'd engines had the accelerator pump to richen the mixture when the throttle was opened, to cover the sudden lean condition caused by more air, before the regular carb jetting mixture function could respond.
In a FI engine of this vintage, the MAP sensor is one of the computer inputs for mixture. And so is the throttle position, both where it is, and how fast it is moving. If the TPS has a problem, even a scratchy area in its resistance, the computer misses the sudden opening of the throttle, so it goes lean, until the MAP sensor input catches up with it.
Gives you some things to check.
A Fuel delivery problem, check fuel pressures.
OR
a tip-in throttle lean problem. Carb'd engines had the accelerator pump to richen the mixture when the throttle was opened, to cover the sudden lean condition caused by more air, before the regular carb jetting mixture function could respond.
In a FI engine of this vintage, the MAP sensor is one of the computer inputs for mixture. And so is the throttle position, both where it is, and how fast it is moving. If the TPS has a problem, even a scratchy area in its resistance, the computer misses the sudden opening of the throttle, so it goes lean, until the MAP sensor input catches up with it.
Gives you some things to check.
Hotshot
Joined: Jul 2002
Posts: 14,285
Likes: 12
From: Bend,OR
before you go buying parts you should pull codes. this motor is efi right?? are you sure plug wire 7 & 8 arnt crossed at the plugs themselves. what plugs are you running and what gap are they at? did you put new clean fuel into the tank? the fuel filter on the frame rail is probably needing replaced as well.
Lead Driver
Joined: Sep 2002
Posts: 9,182
Likes: 12
From: Gateway to the West
In addition to what Kem et al have already mentioned, have to checked your base timing? When you do, make sure the engine is at full operating temperature and the SPOUT connector is removed.
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From: Gaithersburg, MD
the plugs are autolite platinums and whatever gap were on them is on it. i changed the fuel filters. i checked the timing and its fine. i dont have a way to check the pressure currently, so whats some ideas to check the map and throttle position sensor without actually replacing?
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