Got a 4.3 in a 90 blazer...its bad a huge loss of power and if i ever go threw mud or anything and put it to the floor it spits and pops and if i let go of the throttle all the way it goes dead. i have replaced plugs, wires, cap and button. adjusted the throttle body and it had a new air filter...any idea what might be doing this? its a huge huge loss of power and its killing my performance off road

 

cleaning the IAC might be what you need... might not be opening up fast enough as the engine returns to idle...

 

I just went through this. Felt like tranny was going. Turned out to be a blocked cat. Replaced it and now we are back to normal.

 

I had the same issue with a blocked cat.. Then going down the road I heard a pop, looked in mirror, and saw a cloud of black smoke.. Haha. ROLLIN' COAL.. for a second.

 

What were the symptoms of a blocked cat? MY throttle response is in need of improvement and I was considering getting a catco high flow cat from my exhaust shop, but didnt know if I needed to get larger piping also, leave it or what.

 

For me it started with a rattle in the cat. Once it warmed up it would stop. It felt like it was being choked out. No power like the tranny was slipping. Had a hard time to rev it up. Turned out the inside of the cat broke and would block of the flow of air once it warmed up. The code that I was getting was for the MAF (mass air flow sensor). It started fine and ran perfect at low idle. Once I put my foot into it no go lucky to get 30mph. I hope this helps.

 

See Im not getting any codes, but it feels like it takes a while to build up speed/power. Like no pick up when I hit the pedal. It got better once I swapped the oem filter out with the amsoil one.

 

Check EGR valve for carbon chunkage

 

I'll remove it tomorrow and see what it looks like.

 

I'm having a similar issue. I have a 89 chevy s10 blazer 4.3l v6 2wd with model 220 tbi. I changed the IACV, the coolant temp sensor, patched up fuel injector wires, and even changed the spark plugs today cuz they were real dirty. Started it up and it is still popping and running like crap. i also found a hose that got disconnected from somewhere that is severed at one end. However for the life of me I cant seem to figure out where it goes.
http://imgur.com/WfJmI