I have an '86 with a 302FI, auto transmission. I'll try to make this as short as possible.
Over the last couple years, the truck will start good, and run fine, but sometimes, as I'm driving it, when it shifts down as I'm slowing down, and the RPM's drop, the truck starts missing and running real rough. the problem was real bad till the CATS mysteriously dissapeared, then it got better and I thought I had it fixed. But I was driving the pickup a lot this weekend as its the truck I use for ice-fishing and and need the 4x4 just to get around here in the Dakota's in the winter.
Anyway, yesterday, I was coming home from ice-fishing, the truck was running fine, I drove about 50 miles. I came to a town and had to slow down. when it shifted and the RPM's dropped, it started missing. then usually after I manually downshift to raise the RPM's up it will come out of it, but this time it didn't, and it eventually stalled, and I couldn't get it started again. Normally, if I let the truck sit for a while, it will start right up and act as is nothing happened, but I could not get it going today.
I'm used to the 390's and 400's from the 70's, but this 302 seems to be a little weak. I'd hopped it would get better when the CATS dissapeared, but it still seems weak.
The truck otherwise runs good, will start no matter how cold it gets (unless its stalls out first). But this has been going on for a couple of years now and I'm at my wits end.
One a side note, it does have newer plugs and just replaced the fuel filter not to long ago.
It has dual tanks, and seems to act the same way on both tanks.
My next plan of attack is to check the fuel pumps and I was told it may be the idle control motor??
Any suggestions or ideas would be greatly appreciated.

 

Ask the computer what it thinks is going on, this site will show you how:

Ford Fuel Injection

When my idle air control motor dies on my DD Tempo, I think the computer goes into Limp
Home mode, I can't get the thing to go any faster than about 30 MPH. Another time, the
IAC apparently died and the only problem I had was keeping the engine running at idle (had
to slightly depress the accelerator).

In any event, first course of action when debugging a computer-controlled engine is to ask
the computer what it thinks is going on.

 

Thank you.
I unplugged the battery and took it out to keep it from freezing since I had worn it down trying to start the truck. I suppose that cleared all the codes?? I will have to get it running and wait for the problem to occur again and then check the codes??

 

There are two tests:

KOEO - Key On, Engine Off - I believe this contains stored codes

KOER - Key On, Engine Running - Produces codes which are stored

Yes, I believe that unhooking the battery will clear the memory.

 

A clogged charcoal cannister can cause those symptoms. Try driving a distance with the gas cap loose. Excuse to go fishing at least.

Other test is to just drive till it starts giving up and then pull over and open the fuel cap. If you sense the tank was under vacuum when you open it, the cannister is the most probable cause.

Happened to me on a highway trip back in the 90's.