weedog

will a bad catalytic converter on a 2004 F-150 5.4 make it idle rough from 3 RPMs down and smooth out some over 3 RPMS with a slight miss have put new PLUGS and new COIL PACKS and new CAM SENSORS and new CRANKSHAFT sensor and put a new fuel module under the spare tire in it Cleaned the injectors and still same problem does anyone know where to look for the problem Thanks

xMUDKINGx

When was the last time you cleaned your maf and your throttle body?

screamineagle

What brand plugs and coils did you put in?

weedog

cleaned the maf and throttle body today and used champion 7989 plugs and the coil packs was the ones that some on here used but I changed the coil packs out after I tried just the plugs

xMUDKINGx

Any improvement?

xMUDKINGx

Have you changed the fuel filter? How's your air filter? Are your plugs gapped for your environment? Any possibility of a vacuum leak?

weedog

very little improvement yes new fuel filter and air cleaner and plug gap is right I'm going grey headed. thanks again

xMUDKINGx

Don't mention it brother. Sorry I couldn't be of more assistance

weedog

THANKS (xMUDKINGx)

nrivera04

Some will point to the Champion plugs causing your problem. The modular motors seem to be picky about non Motorcraft parts, more specifically the spark plugs. I have no personal experience with them (prev owner had dealership change prior to me buying), but a lot of people would request them when I worked behind a parts counter. Some I was able to sway, others were dead set due the design.