help me out guys 94 gmc jimmy

[bigsmith96]

hey guys having a little problem with my 94 gmc jimmy 4x4 vin w 4.3 (cpi) it has a slight miss at idle and runs fine as soon as u hit the throttle and it runs good and has plenty of power when u stand in it and in mid rang it has no power and u can feel it kinda missing/bucking any ideas ? my fuel pressure key on eng off is around 62psi and 56 psi eng running. it has a cold air intake.my avg mpg is around 10.4mpg with 31/10.50/15 mud terrains
new parts in the last 300 miles...
new fuel pump
new fuel pressure reg
new fuel filter
new fuel line nut kit
new spark plugs and wires
new tps sensor
new starter
new temp sesor
new temp sender
new des cap
new rotor button
new pletum gasket
new catalytic converter
I love the truck just tired of dumping 100$ bills down a wishing well please help me out guys

 

[bigsmith96]

Hmm

Not a single person has a idea ? Thanks for all the help guys

 

[Nando_Oliver]

Does it seem like it's drowning? Had a simular issue with my envoy turned on fine power on idle great to take off but when you stepped on it 4 some reason it seemed to not have any power and rpms would drop almost to cut off I took it to a friend he charged me $50 got a few new fuses and now no probs

 

[Poppasmurf]

Are you running rich/lean (sparkplug color), when you put it under load-like a pull up a big hill- does it buck and miss? When coasting down hill do you get backfire? With having replaced so much it ain't gonna be easy. Are your knock sens OK? At night in the dark with no lights around and engine idling do you get halos around the spark plug wires? Try a remote fuel pressure gauge so you can see it under load while travelling. It might prove a kink in a line or a semi plugged filter in the in tank fuel pump. You'll have to work to isolate it to either fuel or spark

 

[bigsmith96]

Ok

No back fire down hill and yea it misses/bucks when going up hill and the spark plugs look good and it has new wires with no arc at night and like I said only does this at part throttle low rpm and floored runs fine . I'm in the process of puttin in a wide band O2 sensor so that should tell if it's fuel related but I honestly don think it is I'm leaning toward a back pressure issue due to the high flow cat at this point thanks for the replys guys that's y I joined this site and any more ideas will be aprichated