'90 Dak Won't Start when Engine is Warm

[paparush]

My '90 Dak (144k, 3.9L, 5sp) will not start once the engine is warm. Starts on first crank in the morning, or when the block has cooled. If I run it for 15-30 mins and shut it off, it will not start. The motor will crank but will not catch. If I let it sit for 20-30 mins, it will fire right up again.

Any thougts? This behavior just started and may be related to a bad tank of gas. I had a mech pull and dry the tank, blow out the fuel line and injectors and replaced the fuel filter. Still runs rough.

Truck had a new fuel pump installed in 03/2003.

Thanks!!

[paparush]

Here's some additional info - With the truck warmed up but not starting, I definitely have spark at the coil and I definitely have fuel coming into the throttle body. I do hear some clicking when I first turn the key and the gas pedal depresses slightly (by itself)

It's also give an code 13 - MAP sensor or vacuum line may not be working.

Truck definitely runs worse the longer it runs. First 4-5 minutes, it runs great. After 10 minutes its missing, chugging, backfiring and a real pain in the @ss to drive. After 15-20 mins, it will barely idle when still and will often croak if I touch the gas....then I have to pop the hood and let it cool for 20+ minutes, then it will start back up and run will till it heats up again.

Would a bad MAP sensor cause this behavior?

Thanks!

[paparush]

I swapped out the MAP sensor and it made absolutely no difference whatsoever. Going to try to return the $60 piece of plastic tomorrow morning.

What else guys?

Severe timing issue?

Failed plug?

Again, it runs great for 5 minutes then quickly declines into sputtering, backfiring nightmare.

Overheating transmission?

I'm totally grasping at straws.

[paparush]

PROBLEM RESOLVED

I changed the coil, distributor, rotor, plugs and wires and it runs like new. I think the coil was the culprit for as soon as I swapped it, the truck fired right up even though the block was still warm. Now runs smooth at any speed. No backfires, no misses, no hesitation.

I bet the EGR is original to the truck and the o2 sensor probably is too, but I don't want to go borrowing trouble by replacing them.