i have a 96 f-350 crew cab with the 351. just recently it was suckin gas horrilbly, and running rough under load. so i changed the plugs, wires, cap and rotor. same thing. changed the fuel pressure regulator. same thing. cleaned my k@N air-filter. nothing. seems to idle fine, although it never seems to idle down from 1000rpms. checked all the vacuum lines. seem fine. you start to drive, and at about 1500rpms, it starts to bog and run rough. i took off the cataliytic converter and have been running true dual exhaust for the last 6 months, and just recently started running like s**t. there are no idiots lights. does anyone have any ideas? please help!

 

1 test i think will reveale the issue...COMPRESSION TEST!!! i'm only guessing here but seen it before...burnt exhaust valves due to no back pressure that the cat would have provided...this would explain poor milage,high idle and power loss!!!

 

Thanks, I will check it out. Do you think the exhaust valves are shot? or can i put the cat back into the exhaust, and that should get things back on track?

 

check compression at all cylinders and right down the psi for each, should be in the 120psi range...anything under 110psi will likely be a problem and if its well below 100psi then you are looking at an engine rebuild/replacement ...reinstalling the cat now will likely not help...let us know what you get an compression and good luck!