big engine problem, need help

[cooperjd]

1995 chevy s-10, ex. cab, 4x4, 4.3L-W. 126k miles.
this is the problem:
started driving on a 3 hour trip, after one hour it started slightly 'jumping' at interstate speeds~70. like it was missing, but a little more violent than say if a spark plug wire was off. drove more, problem got worse, had to stop after 2 hours and leave the truck in a parking lot overnight. the jumping and bucking got real real real bad and i could not make it home.
what i have done so far:
new plugs, new plug wires, new cap&rotor. the service engine light came on, auto zone guy said it was an o2 sensor. i drove it to the chevy place, and they could find no codes, the light had gone off, and there were no codes in history.
the truck runs almost ok when cold, but will now die on me if i try to drive it and it heats up to operating temps. it misses real bad, like with more than one cylinder, acts as if its not getting fuel, so we think it is getting spark. the fuel pressure is fine, as is my gas. they told me it could be my computer, egr valve, engine valve, or something wrong in my spider (cpi). i completely stumped the chevy mechanic at the dealership, and i towed it home. any ideas??? i am without truck.
thanks a lot
john

[bonecrushins10]

ok a fuel pump can make pressure but have no volume ,

egr vavle is right behind the thorttle body an infront of the distru ,
take it off when its cold spary some panther piss in it an move it with your fingers ,

take the o2 sensors out an also spary them with panther piss , an clean the tips with a old toothbrush

if its pops like a small back fire , than thats a lean pop , most likely a bad fuel pump or filter or a bent valve ,

try running some seafoam thru the fuel system after you changed the fuel filter

get its codes checked again

oh i almost forgot run the seafoam before you clean the o2 sensors

does it run fine when its cold or just slugish an ok

[Jones]

A coolant temp sensor will also cause a dead miss/stumble at operating temp. What's the coil like? How did the plugs read when you changed them? It does sound fuel related.

[cooperjd]

ok, what's panther piss and where do i get it? and i just had my fuel system cleaned. i haven't driven it, and it is parked at my folks house right now, so i'll get back to it friday. what it was doing, running rough but better when cold, when it heats up it misses badly, but like its not getting fuel, not like a bad plug. i do not know how to check the coil, and the chevy place didn't do it. the plugs didn't look too bad when i changed them. if it is a valve problem, would it act up all the time, or only when warm? i will mess with the 02 sensors and the egr valve when i get back to it and see if that helps.
thanks
john

[4Door4X4]

Before you go crazy, test your battery and charging system. I just spent mucho dinero on the exact problem to find out for myself, it was a low battery. It started no problem, ran and drove, but as soon as it reached operating temps or sooner, the Blazer would take a dive. I was getting 116 miles to a full tank, no more, sometimes much less. Low voltage is a computer driven vehicles worst nightmare. Believe it!

Now my Blazer runs great! Good Luck and I hope it's an easy fix.