I have an ?87 Ford F150 with a V8 & 4bbl carb. I have an intermittant problem that strands me in the middle of the road with no notice. After the truck has warmed up a bit, and when I am using very low or no aceleration, the truck will suddenly shut down like somebody turned off a switch. It always restarts (at least so far), sometimes with one or two turns of the key, but sometimes it can take 10 minutes or so, which leaves a weak battery and the people behind me a little upset. I thought it was might be a bad fuel filter, so I replaced it althought the old filter looked fine. No change. I took it to my local mechanic who assured me he could find the problem. When I picked up the truck, they said they could not recreate the problem, so they could not diagnose it. I think the only way I could get the truck to them when the problem was happening would be to abandon the truck in the middle of the road and try to get it towed. Even then, the truck would probably start the next time they turned the key. Short of having a mechanic drive around with me all day, is there something I can check or have them check to keep my truck from blocking traffic?
The most obvious suspect in this case would be the ignition module. Your truck uses the TFI-IV module which was prone to heat related failure.
This module is the little rectangular thing on the side of the distributor. It’s somewhat inexpensive and easy to change.
This site answers some questions about the “why” of this problem.
You can carry a spark tester or timing light so that the next time it does it, you can confirm that it is not a spark problem but a fuel problem. If it is a fuel problem, could be misadjusted float either high or low, debris in the carb that floods or starves the engine, choke not opening all the way or choke pull off. That would be the basic stuff but might just be time to tear the carb apart and put a new kit in. That would take care of the debris and float levels anyway.
Are there any other symptoms when it stalls and starts again like it floods out, black smoke when it starts, technique to get it started again like holding the accelerator to the floor, etc. that could shed some light on the problem?
I had !!! a similar problem with a 1987 E-150.
The solution was to back off the electric choke. This is located on the passenger’s side of the carb. It is a PITA to deal with and it takes a lot of fussing to get it right.
BTW, if the alternator is starting to bite the dust, the electric choke doesn’t back off as fast, and you will wind up with the same symptoms!!