Slick 60's

Didn't see a category for other Fords, so I figured I'd post it here. Got a 2001 Ford F150 5.4 with about 140,000 miles on it. Recently its started to act up at idle. This usually happens when I am at a stoplight. Will idle erratically and sometimes dies. While I'm driving I haven't noticed an issue. Today it seemed to stumble while accelerating from a stop. And it did this today every time i had to stop and start again while at a light.

It previously had the check engine light come on about a week ago and got these codes: P0171 (System too Lean Bank 1) and P0174 (System too Lean Bank 2).

So far i have replaced the pcv valve and tubing, and cleaned the mass air flow sensor. Still has the same issue. Any ideas? Maybe a fuel filter?

Thanks guys for the help.

Duke

Have you checked the throttle body bushings for the butterfly.... thats my stab in the dark Matt !... and why are you idling anyhow ?

Check fuel pressure at the rail.

When was the last fuel filter change?

I would first check for vacuum leaks. Then fuel filter.

A couple that come to mind.....
Dirty IAC (Idle Air Controller) Google it, pretty easy to clean

Bad TPS (Throttle Position Sensor) (but it should be throwing a code for this one)

I honestly dont know when the last time the fuel filter was changed. Not since I've owned it and thats a couple years. I did purchase one and will try to put it on this weekend.

I noticed when I cleaned the mass air flow sensor that the air filter was filthy. I got one of these to and will re clean the sensor after replacing the air filter this weekend.

I didnt think of the throttle body or the bushings. Probably wouldn't hurt to clean that to.

I will clean the IAC, thats a good idea. I'll let you guys know what I find.

So I had a 2001 F150 5.4 until 2007. I only put 75,000 miles on mine but at 65,000 I had to change out the coils due to a rough Idle.


I’d check fuel filter*replace it*. Check air filter *replace it. And if the other things they listed don’t check out- maybe it’s a coil.

I thought about a coil as well but I've had them go bad before and its thrown a code for it. Doesn't hurt to check them though. Thanks for the help.

I've had coils go bad and not throw a code. They are easy to check.