I have a 92 c1500 v6 4.3 L w/ 54,xxx original miles. When the truck is cold, it runs like i would expect it to. once it warms up, it drives like im trying to drive in O/D when i should be in 2nd. needless to say, highway driving sucks....especially up hills! ive changed spark plugs/wires, fuel filter, air filter, coolant temp sensor, temp switch, timing chain cover gasket and oil seal, and poured sea foam into almost every hole the truck has . the compresion in all the cylinders is good (1,2,3,4,5,6 respectively) 190, 210, 190, 190, 190, 190. compression in cylinder two actually went down to about 205 after the sea foam, so i would assume it was just carbon buildup. the timing also seems a little off (i havent actually checked it though) as it backfires a little, and a little more than that after warm.the idle isnt perfectly constant, a little hesitation here and there, but its decent. i hope somebody can help...after two minutes, im just another clunker on the road....lol.

 

interesting....i was just looking at the exhaust a little closer, and it seems that i only have a post converter 02 sensor...i found the connecter for the pre converter sensor, but no sensor to be found...anywhere. any ideas?

 

Just figured I would post my own reply on here in case anybody else runs into the same problem. It ended up being my O2 sensor. Before the sensor warmed up, the truck didn't use the readout from it, so it idled/ran just fine. Once it did warm up and started relaying the wrong info, the computer basically started pouring gas into the carb and threw the timing way, way off along with way too rich of a mixture. Anyway, hope this helps somebody out somewhere along the way...

 

Well if i had of been around . Would of helped.
Glad you figured it out.