Hard start, stumble, and backfiring
 

I have a 96 blazer, and this situation is getting worse. If I leave the key in key on, engine off for about 4-5 seconds, it starts a bit easier, but generally way more cranks then it should take to fire. At first I thought it might just be old gas, but it has continued.

From idle to 1500-2000 rpms, I have a hesitation/stumble leaving lights, etc. if I dont give it half-WO throttle. If im just trying to drive away normally, this issue happens. 99% of the time this is happen from a stop, rarely if ever that I have noticed it while driving.

Just yesterday after replacing the upper oil cooler line, the truck started back firing when I take my foot off the gas and am coasting down a hill. Generally only notice it coasting down hills at speed. A couple of times it was shotgun blast loud. This is being partially caused by a previous owner having a shop hollow out the cat and do an absolutely lousy job welding it back up. It JUST started yesterday, and I noticed it mildly happening this morning, no big bangs this morning though.

I need to fix all 3 of these problems, because all are incredibly annoying. I have been trying to search on the issue of the stumbling, and it seems like everyone tries the obvious tune up parts with no change, so instead of just running out and spending a bunch of money, I want to take this 1 step at a time.

I suspect a fuel delivery problem, so start by following the procedures in this thread and let us know the results.

Thats what other techs at work are suggesting. Fuel pump seems to be the main opinion.