So ran truck tonight without airfilter. Same outcome, although tonight IAT never got to 100 degrees only up to 86 degrees. Still after about 40 - 45 minutes of idling and alittle bit of 15 mph driving around parking lot, engine still just turns off. I say turns off cause no stumble, no hestiation, no sputter just dies nice a calm like I shut it down. What would cause this. I've been debating weither or not to take it to a chevy dealership for a dign. but they told me if I'm not throwing codes then the diagn. won't really help. So i'd hate to just waste $100. Plus I don't trust other people working on my vehicles. Plus I'm a pretty good mech. I build hot rods and cars in my spare time. But this problem I just can't seem to fix and every other car person I speak to can't put there finger on what this problem could be. Nothing makes sense. Lets start fresh. Truck is a 98 jimmy 4.3 W vin 4x4 2 dr with 134000 miles on it. New: battery, alt. ICM, plugs, wires, distr. cap, rotor, K&N airfilter, running proper oil, new high flow cat., flowmaster 40 serious exhaust, new PCV, cleaned EGR valve, cleaned MAF, fuel pump, fuel filter. I seafoamed the engine and I run techron fuel cleaner about once a month or every other month. also run lucos in the oil.

Before the engine shuts off, the truck runs strong as hell, like new, MPG are great. Right before this problem truck was at 180-200 miles with over half a tank left.with mainly city driving on it.

 

What happens if you run with the IAT just disconnected? It doesn't make sense at all to havfe IAT temps of 100* when its 40* outside...

 

If I disconnect it goes to default -40 degrees but I will try that tonight. and runs like crap.

Took to dealership they say fuel pump. Wanted 1300 for it and labor. So does anyone know why a new fuel pump would work until truck warms up then drop to 44 lbs. When it was running at 65lbs. or do I need to just replace this pump again. It's new like 7 months old with about 1000 miles on it. ?????? Also What would the part number be for a 98 4x4 2dr jimmy vin w code. Just want to make sure I have the right one and not the one for a four door in it. And would that make a difference.

 

Ok so changed fuel pump again, this time with a new connector. Truck ran great for about 200 miles. Now today it rained, when to drive to work now truck is missing and stumbling pretty bad at first. Throw random misfire code. Any suggestions why?
Could the plugged cat or the bad fuel pump I had, ruin the plugs? Or anything else for that matter.

 

Possible that you didn't get the tank sealed up and water has gotten in...?

 

Tanks good cleaned, new packing, and pet. Thats good, I'm pretty sure I just got moisture under dis. cap.It only happens on rainy days, then the next day its fine so.But hey thanks for all the help from everyone. Sold the jimmy for$8000. But still have the97 Sub and 00 Blazer. Lookingforward to getting my father-in-laws extreme. Again thanks.