jamus elkins

I have a 99 f250 super duty 5.4. Recently began running rough and the cat was rattling. Long story short, I took cat off, cleared it out and put hollowed caT back on. I have replaced the pcv valve, checked for vacuum leaks, unplugged maf and ran it without the maf and it still ran rough, maybe worse. Tried new maf and made no difference. I have NO check lights on. Took it to auto parts store and ran scan and pulled NO codes. Replaced fuel filter also. Engine bogs down when accelerating, especially at lower rpms. Seems like a loss of power when accelerating but when at cruising speed, it seems to run smoothly until accelerating again. What do I check for next? Bad plugs? How do I check them without taking fuel rails off and manually checking each one? Also the truck idles just fine so I'm guessing my IAC is good.

Simnut

Have you checked your coil/coil pack? Our Explorer had the same kind of issues. I replaced the coil pack and the spark plug wires.....that was the problem! I'm no mechanic.....just something to check is all.

jamus elkins

Well I did a quick test by unplugging each one and each time I did it the engine idle changed slightly so I'm guessing they are working ??? Again I'm no mechanic.