Ford computer trouble... I need help.

[copperdodge]

I have been trying to sell this 1991 F-150 since April. Now it's starting to crap out on me. The other day it threw a check-engine light and it runs like shit. There's thick black smoke out the pipes and it runs like it's on 3 cylinders. It goes down the highway just fine, but won't idle for crap. The transmission is having problems figuring out how to shift, too.

I limped it home from Cobb Co. the other day, and now the guy that I took it to says that he can't pull the code from the check engine light and that the computer's acting crazy. He thinks it's fried.

1. Is the transmission controlled by the computer on a 1991 F-150 with a 5.8 & AOD (I'm assuming this is an AOD, BTW).

2. If the computer is crapped out, what do I do to fix it? Can I get a junkyard replacement?

3. What are my options, since this guys says that these OBD-1 truck computers are hard to find...?

[Eric Brooks]

Sounds like the PCM took a dump. Should not be hard to find at a junkyard.

[mike460]

1. Is the transmission controlled by the computer on a 1991 F-150 with a 5.8 & AOD (I'm assuming this is an AOD, BTW).

No. The AOD was never computer controlled....

2. If the computer is crapped out, what do I do to fix it? Can I get a junkyard replacement?

Might be able to - the problem is that almost every 87-96 V8 Ford truck in the pull-it-yourslef boneyards are gonna be stripped of the motor, harness, and ECM. There are a lot of them still left in the yards, though, so you might be able to find one easier than I think. O'Reilly has them, too about $100 to $150 if you can't find one in a yard.

Good luck Alex!

[copperdodge]

So, the parts house will really have a PCM for $150?? I'll just stop by there on the way to pick up the truck tonight.

I'll tell you though... I am starting to kick around the idea of converting it to a Cummins 4-cyl diesel with a stick shift. Hmmmm....

30mpg from a fullsize?


On a more serious note, lemme put some transmission questions out there....

Before the computer took a dump, I was on 75-north headed to Cumberland Mall (ironically to meet a guy who wanted to buy the truck). The transmission started hunting in & out of overdrive, making the truck start feeling like it was skipping & stuttering. I would give it more pedal and then you could feel it start slipping because it would refuse to downshift. Once you matted it, it would downshift & then bang really hard back into OD.

After I left this guy (who was laughing at me, pretty much), I headed back on 75 and something started shuttering really badly. When I pulled over to look for a blister on one of the tires, I looked down & there was a 16" puddle of tranny fluid and it was POURING out of either the tailshaft or somewhere nearby. Bear in mind that it made this puddle in about 45 seconds. After I had limped it to the guy's shop, I shut it off, and it didn't keep leaking. It's like it needed to be running to be leaking.

One more issue.... whenever I stepped on the gas pedal, the A/C vents (vacuum controlled) would change & stop blowing out of the dash. If there was some kind of vacuum leak somewhere, would the transmission's shifting and the A/C vents be affected by the same leak?


Just trying to figure out what I need to do to this truck that doesn't involve Kerosene & a Match. :cuss:

[Bonz]

So, the parts house will really have a PCM for $150?? I'll just stop by there on the way to pick up the truck tonight.

I'll tell you though... I am starting to kick around the idea of converting it to a Cummins 4-cyl diesel with a stick shift. Hmmmm....

30mpg from a fullsize?


On a more serious note, lemme put some transmission questions out there....

Before the computer took a dump, I was on 75-north headed to Cumberland Mall (ironically to meet a guy who wanted to buy the truck). The transmission started hunting in & out of overdrive, making the truck start feeling like it was skipping & stuttering. I would give it more pedal and then you could feel it start slipping because it would refuse to downshift. Once you matted it, it would downshift & then bang really hard back into OD.

After I left this guy (who was laughing at me, pretty much), I headed back on 75 and something started shuttering really badly. When I pulled over to look for a blister on one of the tires, I looked down & there was a 16" puddle of tranny fluid and it was POURING out of either the tailshaft or somewhere nearby. Bear in mind that it made this puddle in about 45 seconds. After I had limped it to the guy's shop, I shut it off, and it didn't keep leaking. It's like it needed to be running to be leaking.

One more issue.... whenever I stepped on the gas pedal, the A/C vents (vacuum controlled) would change & stop blowing out of the dash. If there was some kind of vacuum leak somewhere, would the transmission's shifting and the A/C vents be affected by the same leak?


Just trying to figure out what I need to do to this truck that doesn't involve Kerosene & a Match. :cuss:

sell it to me for $500 lol


I've only replaced 2 Ford computers in my 17 years in the driveability world

black smoke and transmission shifting weird sound like T.P.S. problem or wiring
check for a broke White vacuum line on the passenger side by firewall "underhood"

or just sell it to me for $500

[copperdodge]

sell it to me for $500 lol


I've only replaced 2 Ford computers in my 17 years in the driveability world

black smoke and transmission shifting weird sound like T.P.S. problem or wiring
check for a broke White vacuum line on the passenger side by firewall "underhood"

or just sell it to me for $500

Thanks for your help! When I pick the truck up Monday, I'll look at that vacuum line. But i might just take $500..... lol.