i have a 95 f150 4.9 straight 6 5speed. my check engine like comes on and off and latley it has been idling really rough and high so i cleaned the air filter and throttle body all that stuff and ran some sea foam it helped with the idling problem a little but also usually when im driving down road in 3rd 4th or 5th and push the peal down it gains speed but it cuts out bad it does itworse once i get up to about 50 mph. it just sputters. i can not figure out what itis i had it scanned at autozone they said there wasnt any miss firing but who knows i cannot figure out if someone could help me thanks alot.

 

I'm no pro by any means, but I'd check fuel filter first, along with checking/changing plugs, wires, cap and rotor. Also, did you clean your IAC while cleaning the throttle body and all that? Also check your timing, could be ignition timing off or the timing gears past their due date, maybe.
Again, I'm the village idiot, so I could be wrong. That's just my initial thoughts.
But with it getting worse at higher speeds, I keep thinking either timing is off or there's something off with the ignition. Could be as simple as spark plug gap being off (should be .044 for your truck) or a plug wire wiggling loose, least that's what caused mine.
Did they tell you what codes popped up when they scanned it? Some numb nuts at a parts store will tell you what you wanna hear for fear of actually having to work sometimes, (no offense to anyone working in a parts store, but SOME people are like that) Hopefully someone brighter than me can chime in and give more direction.

 

idk man today when i started it the rough idleing came back. i cleaned the distributor and i did have 2 spark plugs loose when i checked it lastnight. i tightened them up didnt change anything. the spark plugs and wires have been on there since i got the truck withc was atleast 15,000 miles ago so i might need to change them. everything on the engine is original. i have a 74 5.0 that im rebuilding im gonna do a engine swap sometime next month so i can go through this 4.9. i will say though this 4.9 has got to be the tuffest motor i have ever had. i have put this motor through crap.

 

Did you check the gap of those loose plugs or their condition? I had one back out right after I changed mine and it fouled out with 100 miles, had to replace it because the gap had strectched and it fouled out.
That's the fun part with ignition parts going out, usually have to replace it all together to prevent one bad part from ruining new parts. Had a similar problem with another truck I had before this one, was bad wires. Replaced wires, a week later started acting up again, had to replace plugs. Few weeks after that it started a 3rd time, so I replaced plugs, wires, cap and rotor all at once, no more problems.
The 4.9 is definitely a work horse, mine has 318,500 miles now and I've been replacing part after part since I got it in February. But, every dime I've put into it has came with an improvement, not a money pit like most vehicles I've had.
Oh, one other thing to check is your TPS. I've heard them cause some weird problems (as mine did) all you'd need to check it is a multimeter. Be sure to check the condition and gap of those plugs, you'd be amazed at the difference a few thousandths can make

 

ok now that i think about it the gaps were a little big. i try that and let you know what happens preciate your time