98 gmc safari 4.3 v6
 

Help asap. My van starts and runs fine at first, but after around 30mins of driving it begins to run rough/surge and loses almost all of its power... ive cleaned the EGR valve, it has new plugs, wire, cap and and the and distrubuter is nice and tight in place..

Is this TB injected or CFSI(poppet injectors)

Also, any idea how old the fuel pump is?

Thanks for the reply
 

Im not exactly sure on the injection type.. i can figure that out as soon as i get home. As for fuel pump. I dont know the history on it, so Im guessing its original. That was going to be my next part to change

Most of the time when pumps fail, they won't run at all unless you whack the bottom of the tank. If its the wiring going to the pump(a lot of these vehicles have this problem) once the wiring gets warm(after 30 minutes of run time) they don't pass the current well due to corrosion somewhere. That's what I'm thinking.

I'm also thinking you have the CFSI injection system. Which are junk poppet injectors. There is an upgraded version, cost a little more, but takes care of the idling issues and poor fuel trims.

Verify your fuel pressure with a fuel pressure gauge. Cheap at autozone.

Also, check for codes. There could be a pending code pointing to something.

What Mike said above, plus:

I've seen cars do this when the catalytic converter starts coming apart inside. On one of them I had a "ball" of fractured catalytic converter element sever itself from the rest of the cat on one of my LT1's. It was really a ball, about tennis ball sized. If it happened to be at just the right angle when exhaust pushed it to the back of the housing it would run okay, but most of the time it was turned sideways or thereabouts and plugged off the end of the cat. Took me forever to figure that one out.

Is the check-engine light on?

When the catalytic converter is cool, pound on it once with the heel of your hand. Does it rattle?

Update on fuel injection type
 

Its the "W" vin code, So its MFI i believe.. as for the catalytic converter i hollowed the bastard out. Because it was also producing a dull sulfur smell when it started acting up. It helped the smell quite a bit, But not the performance. Still has a tad bit of smell when it acts up though

Sulphur smell is an indication of it running rich. Probably dumping so much fuel, it chokes itself out.

Hmmmm
 

Any idea of what could be causing that then? I cleaned the EGR valve. But i guess that doesnt mean it would have helped or isnt bad in general..

I'd suspect a leaking injector and/or MAF is really dirty and/or filter is plugged pretty solid.

Still need to check fuel pressure.

I sure hope it's not an injector. Ill sell the damn thing if so. And i cleaned the MAF when i first bought it, it was filthy. That helped 100% when it first started giving me issues. But yeah, ill check the fuel pressure asap and keep you guys updated on my progress. Thank you very much for the help