I have a 1996 4.3 blazer. When i first start it up and try to go if it doesnt warm up, even if it is nice out, it cuts off and has horrible acceleration and doesnt rev any higher. Also when i going about 55mph or even leveling out my gas pedal for any speed the RPM's cut in and out (go up and down rapidly) then it goes back to normal or i just accerate and it goes away. and ideas??

 

Do any codes pop up during this? Have you ever put a scanner onto it and monitored sensor outputs while it is acting up? It could be a problem with the O2 sensor heaters not bringing the O2 sensor up to temperature properly.

When was the last time there was a tune up performed using quality parts? MAF/EGR clean?

 

I havent seen any codes at all and ive never put a scanner or anything on it. I jus recently bought it about a month ago so just trying to debug this darned thing. I think my best bet is just to take it into a shop and get a tune up and have them run diagnostics, because i am in no way a mechanic. But could a fuel pump cause any of that?

 

I would think that if it were a fuel pressure problem, it would have trouble starting and then really wouldn't go away. But you could test the fuel pressure.

 

well it constantly cuts in and out even at slower rpms, usually around 2,000-2,500 rpms, even in just drive, but gets worse in overdrive. It also use to start up right away but now it turns for a little bit and sometime i have to give it a little gas and then it fires up.