2001 supercrew farm

trying to figure out what could cause the running to lean bank 1&2 on my 2001 f150 5.4l and also why it idles rough and rpms jump and the truck shut off at a stoplight when they start to jump any help would be nice been trying to figure of since last winter thanks

bigray327

Lean = not enough fuel.

Eliminate the easy stuff first:
1. Replace the fuel filter.
2. Clean your mass air flow sensor. That thing helps determine the air:fuel ratio set by the computer. That's 3 minutes of work.

If that doesn't help, I'd datalog your O2 sensors. Those also help determine air:fuel ratio, and fail all the time. My (highly modified) Mustang eats O2 sensors for breakfast.

If that doesn't help, think about cleaning your fuel injectors.

serranot

These truck are known for vacuum leaks, especially the hose that runs from the pcv to the back of the intake manifold. Search for P0171 P0174 and you will find lots of threads on it.

2001 supercrew farm

ive replaced the pcv and fuel fliterand cleaned the mass air flow hasent helped

Bryan95

I have the same problem, it only happens when it's cold out

Jbrew

The PCV what? You can only use ONE valve for proper flow. Nobody makes valves with the proper margins other than Motorcraft, - the correct Motorcraft.

The most probable cause for those DTC's are directly behind and beloow the throttle body, - @ the plenum/intake PCV connections. They develop pin holes there over time.

The entire PCV system has to be gone thru and must not take in unmetered air from anywhere. It's a sealed system, so much so, you could store the engine for 10 years and fire it back up again without changing the oil and run with it. But it has to be tight, leak free and have a valve with the correct margins or you eventually screw that engine up. It has to breath by design.

2001 supercrew farm

i havent replaced the whole thing i ment just the hose and yes my truck does it every winter when it gets cold thats it tho summer time runs just fine

Jackedup00

I just had the same issue,I had a newer PCV valve,cleaned my MAF etc,turns out I had a hole in my couple month old fuel line that was sucking in air. So if nothing else,start checking fuel lines.

jprevat

iTrader: (1)

My truck was doing the same thing and my mechanic found a crack in my intake gasket. So mine was doing the exact thing your was.

Jbrew

Yea, that only happens at the intake when someone has staged the bolts wrong. Otherwise, there's not enough torque or pressure to actually break that gasket. All wrench no brain type deal.