p0171 and p0174
 

So my bank 1 and bank 2 are running too lean. The truck will start fine idle okay but after idleing for about 5 mins it starts to surge and eventually stalls if i dont quickly rev the rpms up,

changed the DPFE sensor

changed the fuel filter

cleaned and inspected the MAF looked fine

didnt see or hear any vac leaks

im kind of stumped on what it is, i know my mpg has sucked. any suggestions?

Two possibilities come to mind: intake gaskets and/or pcv valve hose assembly

:stupid:

i did the old fashion intake gasket check by spraying starter fluid around the outside of the gasket to see if the rpms jumped and no luck. and as for the hoses to the pcv assembly they looked good and there was no dryrot or loose lines.

check them again. you have a vacuum leak

What you describe is a typical vacuum leak.

I'd start off by cleaning the PCV with some carb cleaner (or replace it)
If it's not better, let it idle and start looking at the brake booster lines. I'd look at the areas that larger leaks could occur. Brake lines, gaskets, IAC, or maybe the throttle body plate isn't closing all the way?

Rich

my guess is its a PCV hose elbow. seeing as i have replaced enough of them on fords

alright so i just checked the hoses again, and no luck, and after about 30mins of cussing i replaced the pcv valve. and no luck. i serviced the injectors also. is there a trick to checking for vac leaks? i know sometimes you can hear them but is there any way to visually test for them rather than going over every hose?

Instead of using starter fluid, try using a propane torch to "sniff" around the vacuum hoses and upper intake area. The propane gas is more easily drawn into the engine if the vacuum leak is a small one.

I'm still leaning toward it being bad intake O-ring gaskets, although even the propane gas test might not be able to confirm that. Ford re-designed the O-ring gaskets several years back and made them stronger and thicker. See: http://www.rangerpowersports.com/for...95&postcount=8

the truck is still acting up. is there anyway that it could be the MAF?

is it only at idle? sounds like a typical vac. leak, but possibly EGR valve sticking open very little? got a check engine light for anything other than lean code? i know with the pre-01 4.0 they had problems with the intake o-rings, but i thought with the SOHC 4.0 they had eliminated them...

hate to quote my self

Have you checked the IAC valve? Is the problem only occurring at idle?

i dont know if it helps but i had that problem with a mazda mx-6 and it was the air cleaner hose AFTER the mass air sensor dry rotted and leaking. i guess it was letting in air after the mass air already read it so everything was all off