Ok i bought this truck without seeing it. 2000 f150 4x4 5.4l 179xxx miles Got a good deal knowing it needed some work. Truck runs really really bad. Scanned it..said all 4 o2 sensors are bad. But heres the thing the exhaust was cut off right under the fron seats. Has no muffler cats are shot. So i dropped it off today to get all new exhaust put on. Minus the cats. I am wondering if this is the problem of this truck running so so bad! Or could it be a weak fuel pump. Truck sitting runs great when just sitting. Give it some gas...wants to die and has no power. What do you guys think?

 

At 179k miles, those cats definitely should be replaced. If that does not solve it, change spark plugs & wires, fuel filter, O2 sensors, have alternator serviced, check the belts tension, clean the throttle body with carb/TB cleaner, clean the MAF with MAF cleaner only, and clean the intake out. Leaf blower usually does fine, running a cloth through it as far as possible.

 

^ Agreed. Replace cats and clean TB. This is a good place to start.

 

you guys missed 1 thing the op stated......

op i would suggest that the cats be installed on the exhaust that you have fabbed up for the truck or you will be creating more problems down the road. check engine lights due to improper o2 readings due to missing cats would be annoying as hell plus whatever other running problems would develope due to the improper readings giving you wrong inputs to other systems causing them to adjust their inputs to try to correct for what is missing. if you want as your heading states as no back pressure install a set of high flow cats in the system. with your cats being shot as well as 4 bad o2's your truck is already trying to compensate for the bad inputs into it's ecm and it cannot compensate enough obviously causing it to run like poo. i would definitely start there and see how it runs. maybe do a couple other tests on it like comp tests as well as cylinder balance test due to the high mileage you have. maybe even a full tune... plugs, filters, etc.

 

Tune for no cats.

 

Thanks for all the help....i might use o2 eliminators....but i really wont know anything untill monday when he starts working on it...i will keep you posted on how it performs!!

 

Your rear O2s have nothing to do with engine performance, they only tell the computer if the system is running cats. If you engine is running bad it is not because of the rear sensors. The front O2s which measure air:fuel would be a problem if the engine is running lean or rich, replacement of those would be best since they are so aged. Can not put any sims on those, hey are super sensitive.

For a catless system, the very best thing to have done is get custom tuned to run no cats. It does make a difference, it will run better.

 

There ya go! WTF is an alternator service? Do people still actually rebuild them and such? Last alternator we were going rebuilt at the shop, the kit to rebuilt it cost more then a brand new alternator and it was a special order item.