I have an 84 f150 straight 6 4speed manual 4x2 with 90k miles. I purchased this truck a little over a year ago for a good deal. I haven't had to do much to it other than basic maintenance. I am getting ready to order a rebuilt carb because I am positive mine is shot. The truck was sitting for 2-3years before I bought it with very little fuel in the tank. I have been driving it back and fourth to work a few miles from home (about 5 miles round trip) and other short trips. The truck is really starting to run rough and lacks power. Irealise these are not built for speed but it really bogs down going up hill without any load in the bed. I heard that the ethanol blended fuels are hard on the seals/gaskets in the carb so that is why I am replacing it after it was sitting for a few years. The weird thing is that after it warms up about 20 minutes of driving it seems to smooth out and run much better, though it still lacks pickup and power. When it is cold and I first start it up and until it gets up to a good operating temperature, it idles very rough and sounds almost like it has a big cam in it. When I am crusing around and barely touch the accelerator it bucks and carries on. I have to give it alot of gas to get it going, or at least try to get it going. I tried some different fuel system cleaners, Lucas, Seafoam, BG44, but it still isn't running right. I have changed the plugs, wires, distributor cap and rotor, new air filter (about 8 months ago), replaced the fuel pump because the old one developed a leak, and a new fuel filter. I put around 700 miles on it in the last year since I bought it. Any suggestions? Do you think the rebuilt/remanufactured carb will do the trick, or at least help? I also replaced the O2 sensor about 2 months ago. Thanks -Roy

Last night I used the truck to go pick up a kegerator .I havent used the truck for about 3 weeks and I needed to get gas. I drove about 2.5 miles to the gas station, shut the truck off and filled up. When I went to start it it didn't want to start, the truck just kept cranking. I pumped the pedal a few times, and tried again, still it kept cranking. I left it sit for about 3 minutes and tried again holding the pedal to the floor and after a few seconds it finally turned over, it was rough but I finally got her revving. I pulled out and was on my way. After about 10-15 minutes of driving on the highway, and struggeling up the hills I met the guy at another gas station to pick up my kegerator and left the truck idling. When I first pulled in and got out it was idiling a little rough, then after a couple minutes it smoothed out and was purring like a kitten. It was idling nice and smooth at all the intersections on the way home but was still ******* going up the hills and getting up to speed? Thanks again, any suggestions are welcome!

 

I have an 86 F250 with the 300i6. My truck was doing the same thing as you described. Changed rotor, cap, wires, and plugs and it still bogged down.

Then I had a shop set the timing. It was way retarded. Fixed the problem for the most part. I also redid most of the vacum lines. That job looks horrible, but it wasn't that bad.

It sounds like you have a choke problem on your carb. Clean and adjust it and that may take care of the rough runniing until warmed up problem. It worked on mine. By the way, after setting the timing, I was able to peg the speedometer running on the highway. Never could have done that before.

The 300 is a workhorse motor. They are very tough. I have a lawncare/snow removal business and the truck pushes snow with the best of them.

Whitdog

 

How is the exhaust flow out the tail pipe? a plugged muffler or catalitic converter will act like you describe.Check them and let us know.

 

I think my cat is junk, the previous owner put new exhaust from the catback (ofcourse) a few years ago, I would bet my cat is about shot, it is on my list of replacement items. When I try to block the tailpipe at the back I can hear exhaust getting out up near the cat also.

 

No back pressure will get to run like doo doo.

 

It was flooded; probably due to a ruptured accelerator pump diaphragm, or a stuck needle valve, or ... For a quick fix, I'd just buy a reman carb. But the best fix is to toss that POS & drop in an EFI engine. Mine has been running great for over 10 years.

 

I don't know what ppl have against the carbed version it is one of the best engines that there is. If you keep up the maintence you will never have any problems with the engine itself.