Rebornf150

So My truck has done this twice to me now, both times in the morning. i live in Salt Lake City and it has only happened in the morning so i don't know if it has anything to do with the cold.
Anyway, it will start up fine and after i put it in drive and hit the gas it falls on its face and dies, then wont restart. When it happened yesterday I could not get it started for about 15 minutes and then i held the gas pedal to the floor and it fired up. What would cause this?

Any help would be much appreciated.
Thanks, Dan

Oh . . Its a 1990 F150 302L Auto

wde3477

Welcome to the site!

Holding the gas pedal to the floor is supposed to kill the injectors during starts, so suspect somehow somewhere along the way, it got flooded out.

Suggest to get any codes pulled in hopes of giving a better indication - AutoZone does this as a free service. Is the 'Check Engine' lamp working, and has it come on lately, other than for the self-test on start?

Rebornf150

Not that i have noticed. The only time it comes on is after 20-25 minutes of driving but it never has an issue when its on.

wde3477

Might be good to go ahead and see what's causing the lamp to come on - suspect it might be an EGR issue, which shouldn't cause the problems you're currently experiencing. However, if it's a Throttle Position Sensor (TPS) fault, could be onto something.

Does the truck run normally other than this? No stuttering, stumbling, or otherwise missing out?
What general shape is everything in - fuel filter, ignition components, etc.?
Is your fuel good - just wondering with your comment about 'cold' if there may not be some icing going on, restricting gas flow?

Rebornf150

The truck runs fine other than this, and a few things have been replaced recently (fuel filter, dizzy cap, plugs, wires, coil, IAC, o2 sensors) when the truck went through a rebuild 10,000 miles ago.

Im not sure if cold is a factor or not, each time this happened it was in the morning, although i could feel it stumble a little this afternoon but it did not die.

wde3477

A TPS getting flaky will cause stumbling on throttle changes. However, if the throttle is held exactly constant, the engine should catch up, level out, and run fine. Quick throttle changes will stumble more severely than will gradual changes.

I'm puzzled why it takes so long to relight. Gonna have to think about that a little more.

Rebornf150

Thanks for all your help . .

Would you know if a TPS off a Mustang 302 is the same as the one on my f150 302. That would be really handy if it was . .

wde3477

Without looking up the part numbers for each - all I can suggest is that the chances are better than average that it probably would work. Having a look at the connectors may heighten that confidence.

Still going to recommend getting the codes pulled first - the computer should have flagged it if it's not behaving right. No need to blindly replace parts, taking a chance on damaging the donor part, unless one has a high level of confidence.