F150 too lean

Hi guys, my vehicle is a 98 F150 5.4 ltr Triton. I got a check engine light on and the error is “bank 2, system too lean.” I read that this can be caused by a few different things like vacuum leaks or fuel filter and so far I haven’t been able to narrow down which so I want to describe how its behaving and see if anyone can help figure out the problem so I can fix it.
It started with occasional shaking at idle and its happening more as time goes. When at idle it often makes a sound like slurping the bottom of a drink with a straw and shakes intermittently. The fuel economy seems to have gone down. Sometimes it seems like it almost dies in idle, but always keeps running. It runs great when I push on the gas.
Thanks for any help!

When was the last time you replaced the fuel filter? It’s an inexpensive maintenance item and might solve your problem. I’d start there and see what happens.don’t expect the CEL to turn off immediately. It will take a full drive cycle to reset the OBD-II system.

"It runs great when I push on the gas."

That is how a vacuum leak reacts. I suggest you get a smoke test performed. It is the quickest way to find vacuum leaks. Sources of leaks can include vacuum lines, intake manifold gaskets, vacuum switches, and even cracked manifolds. Ford did have a problem with intake manifold gaskets. I had to replace those on my 2000 Explorer. It is also a common repair on the modular V8s.


I suggest you hook up a scanner and check out the fuel trims. It’s possible that both banks are lean. Perhaps bank is not yet lean enough to throw a code

If both banks are lean, you might have low fuel pressure or intake leaks (manifold gaskets, split vacuum hoses, etc.)

If only one bank is lean, it could be a plug, coil or a bad injector

I agree with @BustedKnuckles about the smoke test

Thanks a lot for the suggestions. I’m going to change the fuel filter and get a smoke test done. I’ll report back after. Thanks!