I have a '98 s10 2wd automatic 4.3 X-code; worked fine two days ago, parked it overnight, and wouldn't start in the morning. Cranking just fine - but doesn't fire. After you let off the key it sounds like a knocking noise like it wants to run but won't. Motor shakes and jerks while making this noise.

What could cause my truck to not fire? Any help GREATLY appreciated

 

I had an issue like this. sometimes it would run, sometimes it wouldn't. If it did it was only for minutes at a time.

Turned out to be the wiring harness by the ICM. Check and see if they are pulled out or corroded