1985 F150 302 5.0 carb sensor problem?
10-21-2014, 06:07 PM
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1985 F150 302 5.0 carb sensor problem?
Hey everyone,
I recently tried a forum similar to this one and while it was a great amount of help, I feel I might have wore my welcome out with a 13 plus pages of help.
I will describe the original symptoms as well as parts replaced while on the other forums.
This truck ran perfect up till one day after work, I tried to start the engine (cold) and it fired right up as it always has, but with very rough idle, slight shaking. I figured a vacuum line had began to leak and decided to drive home and fix it then.
I let it warm up as I always do, and put the shifter (automatic) into drive, engine rocked idle slowed while shaking and it died. I did this a few times to make sure it was not something I did.
I again started the engine and it started fine, but with the same rough idle and slight shaking. This time, when I shifted into drive, I held my foot on the gas a bit and it stayed running, but only by working the breaks and gas together, shifted into neutral as I neared stop signs or red light and held foot on gas the whole time,
Got it home and looked over the vacuum lines and they were all in great shape, used carb cleaner all around the carb and intake and found no leaks. So I played with the choke a bit to find no change. I then decided it had to be in the carb as I have owned this truck nearly ten years and never cleaned the carb at all.
I bought the rebuild kit for my carb, took it off and went to work, had it finished in about 3 hours, and back together. Set the carb in place and set it up. Primed the carb, filling the bowls, and started the truck, same problem, rough idle and dies under light load.
List of things replaced..
Plugs/wires
fuel pump
egr valve
timing gears/chain
ignition coil
After each of these were replaced, I found no changes in the engine problem.
I have now decided to test the map sensor, but when I tried to test it, I am getting no power at all to it, book says 4.7 to 5.4 volts should be present when key is in ON position. I was not able to find any voltage at all, grounding off the battery and onto each of the 3 wires going to the map sensor.
So my question is, how do I determine where to get the voltage from? I tried to follow the wires back, they go into the harness and through the firewall. But I lose the wires at that point. Can anyone give me an idea of where to find this problem at? Can I somehow start a new 5 volt line to the map sensor? any help would be great.
1985 F150 302 5.0 carb
I recently tried a forum similar to this one and while it was a great amount of help, I feel I might have wore my welcome out with a 13 plus pages of help.
I will describe the original symptoms as well as parts replaced while on the other forums.
This truck ran perfect up till one day after work, I tried to start the engine (cold) and it fired right up as it always has, but with very rough idle, slight shaking. I figured a vacuum line had began to leak and decided to drive home and fix it then.
I let it warm up as I always do, and put the shifter (automatic) into drive, engine rocked idle slowed while shaking and it died. I did this a few times to make sure it was not something I did.
I again started the engine and it started fine, but with the same rough idle and slight shaking. This time, when I shifted into drive, I held my foot on the gas a bit and it stayed running, but only by working the breaks and gas together, shifted into neutral as I neared stop signs or red light and held foot on gas the whole time,
Got it home and looked over the vacuum lines and they were all in great shape, used carb cleaner all around the carb and intake and found no leaks. So I played with the choke a bit to find no change. I then decided it had to be in the carb as I have owned this truck nearly ten years and never cleaned the carb at all.
I bought the rebuild kit for my carb, took it off and went to work, had it finished in about 3 hours, and back together. Set the carb in place and set it up. Primed the carb, filling the bowls, and started the truck, same problem, rough idle and dies under light load.
List of things replaced..
Plugs/wires
fuel pump
egr valve
timing gears/chain
ignition coil
After each of these were replaced, I found no changes in the engine problem.
I have now decided to test the map sensor, but when I tried to test it, I am getting no power at all to it, book says 4.7 to 5.4 volts should be present when key is in ON position. I was not able to find any voltage at all, grounding off the battery and onto each of the 3 wires going to the map sensor.
So my question is, how do I determine where to get the voltage from? I tried to follow the wires back, they go into the harness and through the firewall. But I lose the wires at that point. Can anyone give me an idea of where to find this problem at? Can I somehow start a new 5 volt line to the map sensor? any help would be great.
1985 F150 302 5.0 carb
10-25-2014, 10:04 PM
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Hi, Thanks for having me.
Everyone keeps telling me to junk this truck and get a new one, I couldn't imagine.
I really hope to be able to get a bit of help here, I am certain it is a simple fix as I can start it up and it will run anytime I turn the kep, but very rough idle and stalls when put into gear.
If anyone here can inform me a bit about this map sensor problem I think it could shed some light on my problems here. Thanks
Kyre Searcher........1985 F150 302 2bl, holley 4bl/spacer
Everyone keeps telling me to junk this truck and get a new one, I couldn't imagine.
I really hope to be able to get a bit of help here, I am certain it is a simple fix as I can start it up and it will run anytime I turn the kep, but very rough idle and stalls when put into gear.
If anyone here can inform me a bit about this map sensor problem I think it could shed some light on my problems here. Thanks
Kyre Searcher........1985 F150 302 2bl, holley 4bl/spacer