1993 4x4 f150 woes

[Blake.]

my dad's 1993 f150 4x4 xlt with the 5.0 and auto transmission has 200,000 miles on it and its starting to act funny.

the symptoms:

while it is cold it runs perfect. cranks first turn. gets up to speed alright. everything works like its suppose to up until you get cruisin about 10-15 minutes down the road at 55 mph or better. then it starts lugging. and the truck is sluggish. the truck rocks back and forth while its happening. not ridiculously. just enough to notice. and its not bouncy like a bad tire. if you drop back down to 45 mph it stops. no shake, rockin, or sluggish feeling.

like i said earlier it only does it once it's "warmed up" so to speak... when you first crank up it'll get up to speed and keep speed no problem. it's about 10 minutes in when this happens when going 55 or better.

 

[Twisted_Steel]

I'd change the fuel filter and pressure check the system.. might be a fuel pump laying down, clogged cat, or a hundred other things. In my experience the EGR valve would make it act funny while getting up to speed also, so I'd start with simple/cheap first.. plugs, wires, filters. Is the check engine light on?.. if so, code scan for older vehicles.

 

[Blake.]

I'd change the fuel filter and pressure check the system.. might be a fuel pump laying down, clogged cat, or a hundred other things. In my experience the EGR valve would make it act funny while getting up to speed also, so I'd start with simple/cheap first.. plugs, wires, filters. Is the check engine light on?.. if so, code scan for older vehicles.

new fuel pump just a couple years ago. and filter when that was changed. i'll ask about the CEL. plugs and wires are happening soon.

the problem isnt getting up to speed its once when your cruising maintaining speed is when it starts.