Ignition/ Timing issues
 

1991 C1500 4.3l
Hello, this is my first thread so take it easy on me.

So my truck was running terrible the other day so i advanced the timing until it ran good (no pinging after advancing). It ran fine until this afternoon. I was getting off the freeway and came to a stop, then when I accelerated to take off it died and it was all i could do to limp it 3 miles home. Now I'm home and it wont run for crap.
When i crank it over it backfires through the intake and exhaust, making me think its the distributor or possibly cps. I just replaced the MAP and ESC sensors within the week. It has a brand new fuel pump in it as well so I know none of those are the problem. Id rather not go spend $150 on a new distributor if thats not the problem.
So I've attempted to advance and retard the timing and try to get it to run but it just wont.

Any ideas? Thanks guys.

Does this motor have a timing chain or belt? Maybe it has slipped??

It does have a timing chain, but i figured if it had broke it wouldnt fire at all. Correct me if I'm wrong though. Ive never messed with a timing chain.

I'm not a mechanic, just dyi guy - but I agree if it broke it wouldn't run. But if it skipped a tooth, it would run badly - and I wonder if you temporarily compensated by changing the timing. Maybe there's a bad tensioner allowing the chain to jump - total guess on my part. My 68 el camino (327) has a chain; gear teeth were nylon and when they wore down the chain slipped and it stopped running.

Im in the same boat as you. I pulled off the ignition control module and im gonna replace that. Its a little pricy but i dont know how to do the chain so ill start with it. If its not the problem i guess Ill check out the chain. Thanks for the help

Don't think the module would cause your symptoms. Try google 4.3l timing chain and look at some other forums

Turns out a new distributor fixed the problem. I think it was the cps that was the problem, but they are internally built into the distributor so you can't replace just the cps (correct me if I'm wrong).
She runs like a champ now. Thanks for the input. Hopefully this will help sombody else too.

Thanks for posting the fix - lots of folks neglect that part so nobody gets any help from their problem.