A little background: I bought a 83 f150 with the 6cyl in it about a year ago. It has run fine… A little rich, but not bad... still ran good. I let the husband of my wife’s friend borrow the truck to haul off some yard waste and this jack a** loaded it up with a bunch of concrete and took it on the highway at about 75 mph. He said it lost power and started knocking real bad. After towing it back to my house, I dropped the oil pan and found 3 of the 6 rod bearings basically gone. I replaced all six and put the oil pan back on (now I got a small leak in the rear darn it... I'll fix it later).
Well, when I started it back up after that, it ran great (this is the first time I’d ever done anything on a car besides change the breaks/filters so I thought I was pretty cool)
So, I went on a test drive and it ran great for about 5 minutes, then progressively got worse… sputtering and wanting to die. I got back to my driveway and noticed that it was running very rich (thick black smoke and fouled plugs). This happened scenario happened a few times. Run good while cool and real bad when warm…
I figured it had to be the choke… well, it’s wide open when it is warm.
Then I noticed the carb was loose on the gasket and the metal tube that connects to the choke was rusted and broke off. That tube goes from the intake to the choke… some sort of vacuum controlled choke?? I picked up a new tube and connected the vacuum line back up along with new gasket and bolted the carb back down.
With all the vacuum fixed, the car now sputters and wants to die all the time.
I took the line from the intake to the choke back off and it runs good again…. Until it gets warm… then wants to die from the rich mixture… I thought about messing with the mixture screw, but it is capped on my carter YFA.
First of all, that tube goes to the exhaust manifold, not the intake. The heat from the exhaust opens the choke. Look for a used carb somewhere on a truck that is running good, or even borrow one for a doy or two. Clothes pin the choke butterfly open and go for a drive. If this is a good carb and your truck is still running bad, than that last haul did more damage than you think.
Think about it. If the main bearings went from overheating, what else went?