my 97 e150 van with 5.4 engine seems to run ok, but the check engine light came on. reset it, it came back on a short time later. took it to autozone, they read 2 codes - P0171 and P0174. can anyone tell me what they mean, and what i need to do about it? the autozone guy didn't look up the codes, but said he thought it meant it was running lean and probably needed an 02 sensor. since the van has 4 sensors, that wasn't too helpful. anybody have better advice?

 

According to my Haynes repair manual:

171--System adaptive fuel too lean bank 1

174--System adaptive fuel too lean bank 2

Hopefully someone esle can tell you what that means.

 

Diagnostic Trouble Codes (DTCs) P0171 bank 1 (Cylinder 1) and DTC P0174 bank 2 indicate the fuel/air ratio is too lean. The fuel trim system is at the rich correction limit.
The problem you have is affecting both banks so it is unlikely you have bad O2s but it's still possible.
You could have low fuel pressure but I think the first thing I would try would be to check for vacuum leaks and for any unmetered air getting into the intake where it's not supposed to......i.e. a loose air intake hose from the air cleaner to the throttle body.
After that I would try cleaning the MAF sensor. If you do a search here with the search button at the top of the page you'll find instructions on how to clean it.
Please let us know what you find

 

thanks for the info on the air leak. i have heard a faint high pitched sound, couldn't decide if it was a hiss or a squeak from the belt. i guess i'll have to start looking around under the hood.

 

ok, finally got above 40 degrees around here, so i ran out on my lunch hour & popped the engine cover on my van. definitely heard a "tea kettle" sound, so i started poking around a little bit & found it. it's coming from a hose which runs from the right (passenger side) valve cover to the back top of the engine (throttle body?). i'm guessing it's the pcv valve system, though i'm not sure (it's been a long time since i poked around an engine). on the valve cover is what looks like a rubber grommet, but above it looks like a black metal or hard plastic ring. when i wiggle the hose the squealing stops & engine speed momentarily drops, so i think i'm on the right track with my lean condition (definitely the van, not me ) anyway, it comes back once i start moving. i drove a bit with the engine cover off & my hand on the hose and it was much, much quieter. so anyway, is this the pcv i'm looking at? the ones i've replaced in the past were at least partially visible; i really don't see it here. i assume its somewhere behind the collar? not sure where i should be tugging. also, if its the hose itself thats leaking, is that a dealer part, or can i get it at a parts store? lastly, will i need to reset the check engine light (disconnect battery) or will it reset itself? thanks guys for all your help.

 

The PCV plugs into the grommet on the top of the valve cover. It should have a short piece of rubber hose connecting it to a hard plastic hose that runs up to the throttle body. I'm not sure what the black ring is you're talking about....maybe a clamp to hold it in place? Take a good look at the hose that runs to the PCV. It could be partially disconnected or maybe split and leaking.

And I wont comment about your own personal lean condition

 

ok, i'm an idiot. what i was looking at was indeed the pcv valve. the ones i've seen before (as well as the replacement i bought) are silver metal, with a flange around the middle to control how far it goes in. the motorcraft one which was in the valve cover was black, & the upper, exposed half was the width of the flange. on a happier note, i discovered that the air leak was coming from the back of the hose leading into the throttle body. the rubber connector is "L" shaped, & it was split at the inside bend. i didn't have time to run out & get a replacement right away, so i temporarily taped it up. i reset the check engin light, and after driving over 300 miles this weekend it hasn't gone back on!
thanks, racerguy, for all your help.