1989 F250 turns off when warm
 

I recently purchased an 89 F250 2wd with a 460 EFI. It has 2 gas tanks. The truck starts up great, runs smooth and quiet, until about 30-45 minutes of driving. Then it cuts out. As its cutting out I press on the gas with little to no response trying to prevent it from dieing. It commonly does this as im slowing down to take a turn or stop at a light.Once it turns off it will start back up after it cools down (it does not ever overheat). This will happen with either gas tank engaged. The sparkplugs, wires, distributor cap and rotor look like they have been replaced recently. I replaced the thermostat, fuel filter and oil since I bought it.

Is there a shut off sensor or a computer somewhere that is telling the truck to thun off at a certian temperature? I could use some advise. Any info would be great!!

Do you have a can of spray carb / coke cleaner? What you can try is to spray short shot of cleaner into the air intake and see if the engine will start even for a few seconds.
If it does, there is a fuel supply problem. If it does not there could be a spark supply problem. That is one way to determine which system could be the problem.

You senario sounds like your ignition coil breaking down and loosing its spark capabilities. If not replaced, I would try a new one. Being a 1989, your engine would like something new anyways.

Remove the cap from the fuel tanks and see if it still does it. You may be pulling a vacuum on the tank and thus starving the engine for fuel.
Eric

Thanks for all the advice! I don’t get to drive the truck all that much, and have to drive it for 30 minutes or so before it acts up so I’ll have to wait until later this week for it to act up before I can try some of the things that were recommended. I may replace the ignition coil before I drive it to see if it fixes the problem. The part is relatively cheap.

I also found that when the truck wants to die I will let it idle for a few minutes before trying to drive it again. It begins to run ok for a while until I decelerate.

Does this bring up any new ideas?

I replaced the ignition coil, the engine coolant temperature sensor, adjusted the timing, and removed the gas caps. The truck still does the same thing.

Any new thoughts....

Remove the cap from the fuel tank to see if you are pulling a vacuum and thus not letting the gas out. You may have a clogged vent on the tank.

Recently got a 89 f150 duel tanks Lariat that did exact same thing initially. I thought it was a fuel problem cause it had sat for 5 years. I had drained all bad turpentine looking bad brown gas out but figured it had clogged injectors...however, a old mechanic told me he guarenteed that it was the catalytic converters (2). He said thr gunk in converter screens, when cold, is in a solid crystaline state and will allow exhaust to pass through. But once engine warms up, this gunk becomes gooey and begins to try and exit out of converter but cannot due to the gooey state and ends up choking off exhaust flow which ends up choking engine to die. I removed both converters and went back with straight pipe to rear muffler. I was careful to leave o2 sensor connection intact so as not to affect that system...runs great but is a little loud but i like it. Its said to affect gas mileage efficientcy about 3-4mpg but thats fine with me...Check it out....sounds exactly like what mine did. I guess catalytic converters that old fail to burn off that exaust residue like it should and it begins to build up and of course at some point , builds up and never gets expelled. Made sense to me....good luck.i cut them off myself and removed exhaust pipes from manifold and took it to muffler shop to have ''Y'' pipe reattacthed.brought it home and replaced old rusty manifold lugs and put that baby back on manifold....then back to muffler

Hey I was wondering if I could get some advice my trucks catalytic converters were cut off and the O2 sensor isn't hooked up to the new exhaust which doesn't have any catalytic converters on it and it's been running really lean and the computer is giving it to much fuel and I was wondering if I cut a hole and put a new O2 sensor on if it would fix the problem? It's an 86 f150. Thank you

Hey man. I just acquired an 89 f150 and I discovered the same problem this weekend. Ran fine when I bought it but drove if a while on a hot day and it cut out. 5 minutes and it started again. 5 minutes later, same thing.

Question is, do I have to preserve O2 etc or can't I just cut the whole deal out and do a straight pipe? wondering about your comment on leaving o2 sensor in place.

thanks.

bert