dss98f150

OK, on my 98 F-150 4x4 Super Cab, the problems started with a P0401, and the truck running rough. Replaced EGR and code went away. No trouble codes in 3k miles. Truck runs rough under slight load, but press on the gas and away she goes. Fuel pressure checks out fine. Plugs, wires, injectors, MAFS, TPS, and Fuel Pressure Regulator all replaced. Every step seems to offer only the slightest improvement. If I pull the vacuum line off of the fuel pressure regulator, there is no change in idle. I've applied separate vaccum to it, and still no change. Bottom line: I'm baffled. Any ideas out there?

 

Freshmeat

I hate do say it, but it sounds like your transmission bands are starting to slip. Find a local transmission shop who does free testing and see what you get. My wagon does that (the trans is beyond blown)- it almost seems to sputter while I'm driving, but if I hit it hard, it kicks down (some times) and goes. I hope I'm wrong, but from what I'm reading, it sounds a lot like what I'm experiencing.

You should have an E4OD, too- most complex rebuild Ford made, yet.

Again, I hope I'm wrong. If you solve the problem, let us know so we can keep it in mind in case it happens to us.

__________________

My Garage

dss98f150

Thanks for the tip FM. The only thing is that when I remove the vacuum line from the fuel pressure regulator, the engine should rev (as I understand it), which really has me looking at the engine compartment rather than the tranny.

Freshmeat

Is it also choppy on idle or just not giving the response you want when driving? Check your throttle cable- may be loose/stretched, now that I think about it. If it is, it won't hold the throttle blade open like it should and your transmission will be thrown off, too. If everything else checks out okay, I'd say look into that... but to be honest, I'm stumped. Keep us updated- I have a couple other random ideas you could try, but I've never seen that before.

__________________

My Garage