99 3.0 runs really rough.
 

stumped on this one. its had the 401 code for quite awhile without issue but now it is running really rough and is very low on power.

we replaced the spark plugs which were pretty much completely worn out electrodes worn down to the porcelin and it ran great for a week then the stumbling came back. We replaced the egr and dpfe and the codes are not reappearing so far but it still runs terribly.

When I checked the fp the guage only showed 25 psi. we replaced the fuel filter and now fuel pressure is 55psi. but it still runs really rough. No codes.

What do we do next?

Sounds like a clogged up EGR valve.

egr valve is new and I checked the port in the manifold

Is it stalling or just reving ruff. If its stalling id check the IAC valve and id check if u got spark to all cylinders too

running really rough, not stalling I wonder if my injectors are clogged or maybe the coil pack is bad? We did not replace the plug wires when we did the spark plugs, do they really go bad? also wouldn't a bad plug wire or coil pack throw a code of some sort?

yeah they really go bad, really. If they never went bad we would never need to replace them. It might not set any codes either.

Yep clogged injector will deffenitly cause it to run ruff. So id clean those out and sea foam the intake as well, my ranger ran alot soother after i ran sea foam. And yeah plug wires can go bad and same with the coil pack. But test each plug for spark and that will well u if its that or not. And i dont think it would thro a code unless it was the coil pack. But just test for spark and see whats what

ok put it on the fancy $1300 scanner from snap on and it basically said the computer was not able to complete its self diagnostic test. what does that mean? bad computer?

I pulled off the plug wires one at a time and ran it and I can't tell that any one cyl is worse than another. This thing is killing me it has to be running by monday....

hhhmmm ok try cleaning the injectors then

I need a cliff to drive this thing off! I had one plug that was arcing out to the head, (i could see sparks around the plug) so I moved it to the next cyl and it did the same thing in that hole so I replaced the plug and its better but still not right. argh I guess I will replace all the plugs again and swap out wires, then go to coil. I will also put some injector cleaner in too, I guess seafoam brand.

Ok hold up. Iv had the best luck with the lucas EFI cleaner. That will clean ur injectors. The Sea foam will clean out the valves, intake and tops of the pistons not so much the injectors but idk it might. But if the injectors are so dirty that there maken the motor run ruff id take them out and clean them with BRAKE cleaner. because the EFI cleaner works really good but over time like on tank of gas. It sounds like ur needed to fix it quick

If it's arcing to the head it's the spark plug wire (boot) not the plug, and that will make it run bad every time. You had better quit throwing parts at that thing and go get a new set of wires, and if it does it very long it can burn the coil up.