Hello folks, recently picked up a 98 B1500 shorty with the 3.9. Ex-Verizon wireless utility van. I honestly hate Chrysler products (long story) but it's serving me better than my last truck for what I do for work.

Anyhow, I'm having some issues with it. When I'm going down the highway, it'll randomly drop power, feels like its running out of fuel or dropping a cylinder, and some backfiring. It got bad enough that I actually had to pull off the road and let it idle out for a bit before I could drive again.
I've done a full tuneup (plugs, wires, cap, rotor, pcv valve), air filter, oil change, replaced the TPS, planning to clean the IAC next time the weather is 25+, and the problem has been mostly eliminated. However going down the road today it did do it once more, though this time it was extremely brief and almost unnoticeable, thought it was the road at first.

What else can I check on and replace? I haven't done a compression or fuel pressure test yet, as 99% of the time it runs just fine and hauls down the road as best a V6 powered tube possibly can. Am I looking at a fuel issue, failing sensor (crank?), or something else? I've already browsed through all relevant threads in the 162 pages of the van section, which is what led me to replace the TPS.

Any help is much appreciated.

 

Sounds like the fuel pump is starting to fail. Try to take notice if it cuts out with more or less than 1/2 a tank of fuel. If it only does it under 1/2 a tank then it is the fuel pump.

 

Update on this situation. I replaced the pump with a known good unit, the problem still persisted. Long story short it ended up being a transmission problem. Torque converter was locking up early and staying locked up. Ran some Seafoam TransTune through it, it made an instant difference. Finally did another can, followed by a filter and fresh fluid. By god that thing actually feels snappy now. Unfortunately I need to drop the pan again and use RTV on the next gasket. This one didn't seal completely, I got a leak.