Just did an engine swap on my 98 blazer 4wd 4.3 vortec. Pulled the engine from a 2000 bravada awd. I was driving the bravada for a couple months it was from up north had a lot of rust under it just needed the engine. Swapped the engine and now it's like the cat is clogged but it doesn't have one and does not have a muffler, all that was stolen when it was at the tow yard. The blazer sat for about 5 months so I'm sure the gas wasn't great but I've added fresh gas a few times with additives and nothing so far. Plugs,wires,cap,rotor and fuel filter are all new and fuel pressure is good checked all vacuum lines pretty sure all good hooked them up as they were. Really at a lost at this point today I tried 2 more cans of seafoam tried a different coil and ignition control module.

 

Any codes?

Do you have a scanner that displays live data? If so, are there any misfires when you try to accelerate?

What do the fuel trims look like?

Have you performed the fuel pressure tests in the sticky?

How old is the gas?


George

 

Are all sensors hooked up properly?
O2 sensor? (as you said cat got stolen...)
And what is the ignition timing?