Cannot figure this one out

[wlsnoops]

Greetings,
95 S-10 Blazer 4.3 L
Several weeks ago the vehicle started sputtering like the timing was off. Checked out okay. Started running rougher. Finally started stalling and now will only start and then die immediately.
Error code read a problem with the IAC. Changed that with same result. Changed the fuel filter, but fuel pressure wasn't the problem.
Took it to a (I thought) reputable mechanic week before last. He asked me if I might have put diesel fuel in it. No, I didn't do that. He said it could have been bad gas. Told me to run a tank of premium in it. I filled up with premium and added some dry gas to it. Ran a little better at first, but still sputtered and eventually got worse.
What am I missing here? The consensus with people that I've talked to is that it is a fuel related problem.

[MT-2500]

Originally Posted by wlsnoops

Greetings,
95 S-10 Blazer 4.3 L
Several weeks ago the vehicle started sputtering like the timing was off. Checked out okay. Started running rougher. Finally started stalling and now will only start and then die immediately.
Error code read a problem with the IAC. Changed that with same result. Changed the fuel filter, but fuel pressure wasn't the problem.
Took it to a (I thought) reputable mechanic week before last. He asked me if I might have put diesel fuel in it. No, I didn't do that. He said it could have been bad gas. Told me to run a tank of premium in it. I filled up with premium and added some dry gas to it. Ran a little better at first, but still sputtered and eventually got worse.
What am I missing here? The consensus with people that I've talked to is that it is a fuel related problem.

W or Z engine?
How is the tune up end?
How many miles on plugs and wires and air filter.
What brand of plugs?
Any engine miss?
Have you ran a fuel pressure test on it?
Any other codes or check engine lights?

[Blind]

if your fuel pressure is good, check the coil, try swapping the coil with a known good one. Engines take 3 things to run, fuel, spark, and compression of air.

when the coil went out on my old `97 sierra it still gave good spark, all diagnostic's came up with nothing, it was sitting at a shop for a week until my brother could come over for a visit, he has a `96 tahoe so we started swapping sensors and parts...maf...no...coil..bam!

FYI - the coil was giving spark out of every plug wire, but it apparently was not enough spark.