back fire when accelerating

the blazer will not accelerate uphill and back fires. I changed the fuel filter. sounds like a vacuum problem but i don't know what to look for?

Not to be coy, but you would be looking for a vacuum leak. If you have a guage, you need to see what it is first, 17-19 in/hg.

Some people recommend spraying around the hoses with WD-40. When the leak is found, the idle will smooth out.

What year is this and the engine would also help.

the blazer will not accelerate uphill and back fires. I changed the fuel filter. sounds like a vacuum problem but i don't know what to look for?

Please supply your year, model and all your maintanence history.

Do not ask for help with a general question with no information.

the blazer will not accelerate uphill and back fires. I changed the fuel filter. sounds like a vacuum problem but i don't know what to look for?
1985 blazer 2.8 6 cyl manual trans. 4x4. I changed the fuel filter, seemed to run better for awhile but problem still exists. I bought the blazer in Colorado used this past summer. I will try the 17-19 in/hg. and look for the leak.
I also would like to know where the oil pressure sensor is located. Do I need to replace the carburetor? Thank you for all your help.

Ok, you have a 2.8 carbed. The first thing to check is timing, sounds advanced if your backfiring through the carb. Disconnect your vacuum advance and plug the hose and set your timing using #1 cylinder. Now, after your timing is set, remove the timing light from the #1 wire and put it on the #4 wire, the timing mark should be the same. What you are checking is timing chain stretch.

Now, before doing all of this, and since you purchased the truck used, have you done a tune-up? Like plugs, wire, cap and rotor? It should be done first.

True, a tune up should be the first thing to do.

As Mikado said time the vehicle first with the timing wire disconnected from the computer and check to see what it is.