Hopefully someone can give us some more ideas as o haven't found a mechanic that has a clue. Began about a year ago with my 09 platinum 5.4 occasionally having a slight kick, or hesitation as I would come to a stop light, hard to explain but felt like a hard downshift. We had it scanned and no codes came up, it progressively got worse. I had the plugs changed, no better. Finally got a code for 02 sensors and guy told me the cats were bad and chose to remove them as we don't have emissions check here. Also at this point added dual exhaust. Now about three months later the bucking at sowing down is worse and also every morning afte I go tough my first stop sign in neighborhood it won't shift and I have to shut the truck off and restart, upon googling this maybe fords limp mode?? I apologize for the long post but have had it at about 6 different mechanics and few transmission shops with no success. Last thought is to put the cats back on and take to ford as some have suggest that could be computer malfunction. Only mods to truck are level, 33 mud tires, cold air intake and magnaflow exhaust. Also truck just has no power and fuel economy is terrible , when I Shift to reverse it just sits and doesn't do a thing until I press the gas.
Thanks!

 

I don't see how it can't have codes if the cats are removed. You should have a constant P0420 and P0430. It should also be running too lean if you have an aftermarket intake without a custom tune.

Put the cats and stock intake back on and take it to Ford.

 

I apologize. It is showing codes for the cats, just nothing else. Was running bad before removing the cats with no codes is my only concern. Seems you are correct. I'll just put the cats back on and take it to ford. Do you think it's necessary to remove the k&n cai also? Is that just what ford is gonna say when I bring it in??
Thanks for the quick reply

 

There is a known issue with K&N and other aftermarket intakes on the 5.4 3 valve - they throw the MAF calibration off and can cause the engine to constantly run lean unless you get a programmer and a custom tune for that specific intake. Better to be safe. Ford won't complain about a cat-back exhaust.

FYI, the stock intake is more of a cold air intake than a K&N - it draws air from the fenderwell, not under the warm hood like the K&N. The K&N filter can also let through more dust and also possibly oil foul the MAF. Have you ever cleaned the MAF? That can cause it to run like crap.

 

Thank you. I'll replace the intake and clean the maf. If not better then I'll take it to the dealership. I appreciate the advice!