I have a 1997 F-150 with the 4.6L and it has been running very bad latley. I was pulling a 6X10 trailer for around 50 miles, unloaded it, and right before i got home with it empty my truck started shaking badly and came close to stalling a few times. The codes it is throwing are as follows:
P0401 EGR Flow Insufficent
P0420 and P0430:Catalyst Efficiency Below Threshold Banks 1 & 2
P0301, P0304, P0305, P0308: Misfire on cylinders 1,4,5 and 8
P0171& P0174: System too lean banks one and two.

The EGR flow has been a problem since i bought the truck 3 years ago and i have replaced the EGR valve twice with no luck.

The truck is creeping up on 236,000 Miles and i would like to keep it running but i have no clue what caused all the problems.

Any info would be greatly appreaciated!

 

the egr problem is most likely a bad dpfe. get that replaced and see what happens.

have you ever replaced your o2 sensors? if not, pick up two and replace the ones closest to the engine on each side.

when was the last time you replaced your plugs, wires, and coil packs? if it has been at least 60,000 miles then it is time.

if all of the above stated needs to be changed, go ahead and do it as soon as possible. i think everything will be running tip top after this service.

 

The plugs and wires were replaced about 10,000 miles ago. There has never been a problem with the motor till now.

 

Check the PVC elbow at the back of the throttle body and check for vacuum leak in general Sounds to me like you have a major one.

 

Not sure if it makes a difference but the pvc filter has a lot of suction still but I will check it out tomorrow morning.

 

dont worry about the cat eff codes, they can't filter correctly with the engine going into lean conditions. I say dont worry about the codes, I mean dont replace some parts b.c of those codes. Do worry about it tho because if you dont correct your other problems, the cats will eventually burn out and you will really have those codes, not just the "false readings"