I have a 91 chevy C1500 4.3L V6. I started having issues with it bucking every now and then about a month ago. It eventually got worse and then died on me. After that I could start it but it wouldn't idle and would start bucking and cut off. I rebuilt the throttle body thinking maybe it had to do with that but that didn't help so I sent it to a mechanic. They replaced the distributor (crack in it) and put in a new computer but it still did not fix the problem and sent it back to me. I noticed the timing chain was in bad shape so I replaced that, fuel pump, fuel filter, gear set, coil and plugs and wires but still nothing. I took the vacuum hose off the map sensor and plugged it with my finger. The idling got a little better so I replaced the map sensor. It was a little better but it STILL will not idle and keeps cutting off if not kept reved up. I really don't know what else to check or replace. Do you have to program the computer? If so, how do I do that. Any suggestions or input would be helpful.

Thanks

 

Did you get it scanned for codes?
To reprogram the ECM... You'll have to take it to the dealership to get it reflashed. BUT I WOULDN'T

 

Your truck does not have a reflashable EE-prom in it. It still has a replaceable prom in it.
After all that has done you should take it somewhere with diagnostic equipment and start from scratch. It is possible some part you replaced was bad, when new, and your chasing your tail at this point. Scanner, fuel pressure gauge and timing light are some of the items you need for proper diagnosis.

It's possible that you have a burnt valve but I don't recommend pulling the heads with out proper diagnosis.

 

My bad
I just learned a couple of days ago, some can NOT be accessed and tuned or flashed
Thanks Dan

 

No problem, I am not trying to offend anyone just trying to inform.
Sorry if I come across that way.