Hello!

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.

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)

One other thing, I'm getting and Engine 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.

Any ideas before I turn the truck and my checkbook over to our local dealer?

Thanks!

 

I was going to suggest the starter, but you said that it still cranks. Sounds like a sensor problem, possibly a coolant temp sensor or something around those lines. Definately need to get it on a scope to check the individual sensors.

 

J-,

Thanks for the reply.

Do you know offhand if a failed MAP sensor would affect the performance to this degree?

Thanks!

 

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.

 

under my best advisement, take it to a mechanic, problems like this can be anything from the computer to a stupid senser, the result is , you could dump 400 dollars in it and not remedy the situation, then spend 65 dollars an hour for a mechanic to fix what you missed, my guess is if you changed your mass airflow pressure sencer, you might wanna check your egr, if its clogged it could be the culprit

 

another thing to check is fuel filters lines and, makeshure no one hates you enough to put a ping pong ball in your gas tank

 

Mudkicker,
Do you know which sensors monitor the engine temp? Seems like some sensor is no longer realizing that the engine is warm and its flooding too much fuel into the chamber.

Just my W.A.G.

 

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.