2001 Ford explorer lean codes

2001 Ford explorer p0171&174 codes.I replaced intake gaskets(orings) pcv valve and egr.fuel pressure hovers around 40 psi, kind of low I think.when I accelerate ltft goes from +24 to +14 but the stft spikes from + 12 to over 20. When I smoke test it it has a small leak underneath egr.What would trims look like with a small vacuum leak and low fuel pressure? I just need to get this pass inspection ! It has no drivability issues or maybe I just got used to them. Tia!

Not having any luck finding the culprit! 2001 Ford explorer 4.0 sohc,replaced intake gaskets all hoses from intake,pcv valve egr valve.Ltft in the 20s gets better on acceleration.Smoke tested multiple times no leaks. O2 sensors oscillating between .2 -.8 react well on acceleration.What am I missing?

Check the freeze frame data for the lean code to see under what conditions the code sets. Then you'll have a better idea if you're looking at another vacuum leak (low RPM, low load) or fuel delivery (higher load, RPM) and under what conditions to test.

Noah gave you a valuable advice.
Furthermore you may want to look at the FUEL VOLUME that the pump is providing.

Wouldn't low fuel volume make trims worse under acceleration? Mine gets better like vacuum leak.

What kind of vacuum leak won't reveal itself with smoke test?

1 -
The fuel trims you reported do not get better at acceleration ifyou lokk at the total fuel trim....


2 -
An internal vacuum leak does not show up with a smoke test.

Butchfuch wrote: What kind of vacuum leak won't reveal itself with smoke test?

A tricky one

Like Juergen pointed out, an internal vacuum leak may not be evident with smoke. A purge valve partly sticking or an internal brake booster fault wouldn't show smoke either. The flow gauge (if equipped) would still indicate a leak even if you can't find smoke.
Certain gaskets may only leak when cold.
Too many variables, that's where the freeze frame helps point us in the direction of the next test.


As Juergen also suggested, a fuel flow check will help eliminate a pumping delivery issue, and depending on the conditions the code set, you may want to to do a "flat-rate test drive". Record up steam 02 sensor activity during a wide open throttle pull through first gear to get an idea of fuel delivery.