I have an 87 2.8 blazer which started popping like it was backfiring. At first it was just under load (up hill) then it started doing it all the time. It has new plugs and wires, new throttle position sensor fuel pump and filter. Have not had it coded on anything. Yesterday I changed the coil pack and it ran the same on know my way to work( about 40 miles) then on my way home it ran great until half way home. Started doing the same thing again. Once I got home I run to town and then it happens, it dies! I try to start it and it just turns and turns. I have to hold the gas pedal down to get it cranked and rev it up to keep it running, once I stop it dies. So I got it home, finally after shifting from neutral to drive and revving the motor the whole way. Once home I looked under the hood and smoke was coming out of the throttle body, I think out of the tps. It is also blowing back up through the throttle body. Ica see gas

 

What brand fuel pump was installed? Yes it matters on these trucks.

 

Im not sure, can't remember or find the receipt.

 

OK,where did you get it?

 

Backfiring under load then slowly getting worse starts to sound like a clogged cat. I know the factory one on mine clogged 2 years ago. It started acting up like that. Have you pulled the codes to see if its got any stored. If the tps went out like that it should have thrown a tps or some o2 code.

 

Cut the cat off and still the same

The fuel pump came from advanced auto

Now it wont start at all. Lot of fuel blow back on the throttle body. Changed icav and nothing. Does it have a maf sensor?

 

No maf.


Still haven't pulled the codes?

 

My '85 Jimmy T15 w/2.8 acted the exact same way you're describing, and it was a broken wire under the insulation of the coil connector causing the problem. I bought a new connector to replace the old one and no more problems. I'm not saying this will fix yours, but it is something to look at and a cheap fix if it is the problem.

 

You might have a bad pump,the pump you got from advance auto is probably an airtex,which these trucks HATE. only route is an ac delco or delphi brand replacement.

 

I had the same problem. Mine was the gap on the spark plugs was too close causing premature fire and popping out the TBI.