aliens8mycow

This is my first post here. I've been reading through old threads looking for info with no luck.

I have a 91 F150 with 5.0L and AOD trans. Just bought it so I don't have much history to share.

It runs like a champ until it's been at highway speed for awhile, then when you slow back down it can't seem to find a gear - it bogs, jumps, etc. and won't get out of it's own way. The strange thing is, you can pull off the road and shut the thing off, restart it, and it'll drive fine until you reach highway speed and then slow down again.

Thanks for any advise that you can give - Please tell me that this is a sensor or some other cheap/simple part!

aliens8mycow

Maybe a little more info...

Several other posts that sound 'similar' seem to point toward the fuel pump, MAF sensor, etc. Could this be electrical? The only reason I think that is because I can shut it off and restart it (without waiting for anything to cool off) and it runs fine for awhile.

I hate to break down and take it to a shop if I can handle it myself, but I'm not sure where to start.

Just call me Sean

iTrader: (1)

Check the computer for codes. Detailed description of how in the maintenance section under "Diagnose trouble codes".

aliens8mycow

I don't think it's throwing any codes... check engine light has not come on.

Knowing my luck, the bulb's probably burned out!

I'll investigate and see what I can figure out.

Just call me Sean

iTrader: (1)

The check engine light doesn't always come on, and sometimes it comes on momentarily and you may not have noticed it. There can still be codes in the computer even if the light isn't on. The light should come on when you start the truck and then go out, so if it doesn't then the bulb is probably burnt out.

aliens8mycow

Thanks for your help (and patience) so far... as you can tell I'm not a mechanic!

The check engine light does work. It only comes on when you try to keep going and the engine dies, though. The more old threads that I read through, the more directions I want to follow. It seems similar to fuel pump trouble, and this truck does have dual tanks with only the rear one working. The gas guage is also inaccurate...

It sputtered several times this afternoon, and I'm dropping it off at a local shop - I think this is far beyond my abilities.

aliens8mycow

As we go through the process at the shop, I'll let you know what the diagnosis is. Maybe it'll help someone else with the same issues. Hopefully I'll find out what they want to do on Monday.

aliens8mycow

Turned out to be the fuel pump... While the tank was out, we replaced the pump, wiring harness, sending unit, filter, even the rusty old tank. That cured it!

DarkNite

Good to hear you got it straight.