Questions and Answers

Poor Running F-150 Q. Hello, I just purchased a very poorly-running 1984 Ford F-150 4x4 with a 351 Windsor, 4bbl carburetor, and an automatic transmission about a week ago. I checked the compression before purchasing it, and it shows over 100 lbs of compression in each cylinder. The price was right at $500, so I went ahead and bought it.

The previous owners bought it about 6 years ago, and it wasn't working well then either. They spent over $2000.00 getting the transfer case rebuilt, and stopping various leaks. They are not very mechanically inclined, and basically let it just sit there for several years.

There are two basic problems. First, the transmission, a C5, is extremely inconsistent. I've never had an automatic transmission before, so I am not very familiar with them. Occasionally I can put it into gear without a problem, but sometimes when I start it and put it into gear it just grinds. The clerks at the local parts store suggested that it may just be dried up seals, and that I should try a "reconditioning" additive.

When I changed the transmission fluid, I noticed that it looked like someone poured a full bottle of glitter into it, so I'm thinking the problem is pretty bad. Also, when I actually get the engine running (see the next problem) I can drive it (very poorly) for about one or two miles, then it slips out of gear and grinds. I plan on pulling it and replacing it with a rebuilt one later this summer, so I'm pretty sure that will fix the problem.

The other problem is more confusing to me. The engine starts beautifully every time, whether it is cold or warm out. However, after about 30 seconds or so, it just dies. If I get it into drive before that 30 or so seconds is up, it dies. I can, however keep it running by tapping the accelerator pedal several times. I can tell that someone had played around with the vacuum lines before, because the EGR ported vacuum switch ports are broken off, and the EGR vacuum hose is going straight from the EGR valve to the solenoid. I've tried disconnecting and plugging this line and the solenoid port, but that didn't seem to change anything. I have a new PVC on order, and will get it replaced soon, but it doesn't seem like that is the main culprit.

When the engine starts to die, I can play with the accelerator pedal and revive it for a short time until it tries to die again, and I tap it again a few times, and it comes back, etc... I can do this all I want to keep it running. I replaced the fuel pump, but that didn't seem to help either. After replacing the pump, I found two interesting things, When the engine starts to die, if I spray some carburetor cleaner down into the carburetor, it comes back; and, if I hold the butterfly tightly closed, the engine seems to idle perfectly (at least while in park).

I haven't tried putting it in gear with the butterfly tightly closed yet, I'm not really comfortable with that. Could this be a bad electric choke? Bad dashpot? Bad vacuum solenoid? Bad carburetor base gasket? How do I test the choke, dashpot, solenoids? And is there any chance that a vacuum problem could be causing the transmission to fail intermittently?

It seems like there are so many possibilities, I guess I'm really looking for a place to begin.

Thanks,
Deb

A. Well Deb, it seems to me you have a major vacuum leak somewhere. If you can completely close off the choke butterfly and the engine still runs, and run substantially better, you have to have a vacuum leak.

The first thing you have to do before you can test anything is to get the vacuum leak figured out. First off, replace all the vacuum lines and hoses. Pay particular attention to the PCV hoses. Then with the engine running, lightly spray carburetor cleaner around the intake manifold gasket and the carburetor base gasket. When the engine picks up rpm's, you found your leak.

If you don't find anything external, and I'd be very surprised if you don't, then the carburetor has an internal vacuum leak or is plugged up with gum and varnish from sitting gas. These carburetors can be rebuilt, but I would recommend buying a rebuilt carburetor.

100 pounds of compression is low for that engine. I would expect to see about 180 pounds in that engine. If the truck has been sitting for as long as you say, the compression may come up some as the runs in again.

As for the transmission, you're right. It's gone to that great transmission shop in the sky. You can get a rebuilt from a lot of places or get a good used one.

Keep me posted on your progress.

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