I have a 1998 chevy blazer..it has a 4.3 vortec..just a couple days ago it started backfiring and stuttered when it hit 50 mph...i changed the cap and rotor and still no change i changed plugs still no change..ever since we had it ive never had to lift the hood except to change oil and the nesscesary parts...im really wanting to drive it again..and stop using the car ..the cars to small i like stretching out and having room...so any info is helpful..ppl tell me the pump is bad..some say the filter..others say timing but i dont think its the timing..cuz it still starts just fine and idles till it gets warm then it starts cutting out like and idle problem and when you rev it to 3 grand it stutters all the way there...help..lol

 

If you're hitting a problem at 3K PRM, fuel delivery may be the problem.

Consider this: there's a fuel pump pushing lots of pressure. If the pump wasn't running, the car wouldn't start. But fuel has to flow through the filter. Filters are pretty easy to change - I'd try changing the fuel filter.

And there is pressure in those fuel lines - don't just pop the filter off. There is a pressure release valve in the fuel lines coming off the intake manifold on the driver's side. You'll have to remove the air intake assembly (just follow it from the air filter) from on top of the throttle body to see it. It's toward the back of the motor and should have a black plastic cap screwed onto it. Unscrew the black cap (don't lose it), wrap a rag around the lines, and press the valve with a fingernail. You'll spray some gas around but it releases the pressure in the fuel lines.

If the filter doesn't do it, I'd take it into a shop and have them run a scope on it.

 

ok thanks..ill try that hopefully it does the trick..but i also have to replace the plug wires..cuz when i went to check the plugs.it seperated in my hand..

 

Very important to rotate the rubber boot first, before removing a plug wire - and then to pull only on the boot, not the wire.

However, sometimes the darn things just break! Look at it this way - it may run better after replacing a wire that was marginal.