p0171 lean condition

[JonnyHightower]

I have a CEL P0171, lean engine condition in a 2000 Ranger, 2WD, 2.5L, manual, with 80K miles. I've noticed a low rough idle, especially just after I depress the clutch and take it out of gear into neutral. Doesn't stall, and the idle recovers pretty quickly.

I REPLACED: spark plugs and wires, PCV valve, upstream O2 sensor, MAF sensor ($$dealer$$), fuel filter, air filter, and gas cap. I ran several Techron bottles through the engine, SeaFoam'd it (top end, intake clean), and have been running plus gasoline for awhile. I tried to test the EGR by covering the EVR solenoid hole during idle (to establish vacuum). The engine nearly stalled, which suggests a functioning EGR (according to YouTube).
SPEAKING TO VACUUM LEAKS: I ran some propane along the vacuum lines with engine on and didn't hear any change in idle. A homemade smoke machine produced a little bit of smoke from the IAC valve. Normal?
SPEAKING TO FUEL PRESSURE: I measured fuel pressure on the rail. Key on engine off pressure measured within spec. Fuel pressure increased ~5 psi (to 68 psi) when I turned on the engine. Chilton predicted a drop in pressure when starting the engine. I don't know the significance of that yet. Chilton suggests using a handheld vacuum pump to further investigate, but I haven't reached that yet.
SPEAKING TO READINESS TESTING: Scanner picked up a failure: "delta pressure for downstream DPFE hose test." Might be causing my CEL? Is there a quick test I can use to test the function of the DPFE itself?

Taking the above into account, does anything stand out as a possible cause? Suggestions? Quick tests that I can do to narrow it down?

 

[Mazda]

Have a look at this site. Has help me and others before.

http://easyautodiagnostics.com/ford/4.6L-5.4L/how-to-test-the-egr-system-1

I would assume the the DPFE is bad. Check the hoses first. They sometimes slip off or get cracked from all the heat from the EGR pipe. They are a special silicon hose so you will need to order it online or the think napa has them.

I don't know what you paid at the dealer for your MAF but here's one: http://www.rockauto.com/en/moreinfo.php?pk=5034582&cc=1362765&jsn=542 $55.00

Bryan

 

[adsm08]

A bad DPFE won't set a lean code. If anything it will set a P0401, insufficient EGR flow.

What do your fuel trims look like?

 

[JonnyHightower]

To Mazda,
I paid WAY too much (~$600) for the MAF sensor replacement. I was originally at the dealer for suspension repairs, and the truck made awful noises on the drive home. Went right back in (mistake perhaps) and the dealer sold me a MAF sensor. CEL came on not long after that episode, and I can't help but wonder if it arose from something they did (can't be sure, at least not at my experience level). Thanks for the link. Looks like it will come in handy to identify the DPFE problem. The readiness test is pointing at a DPFE problem, so I'll investigate that. If adsm08 is right about the DPFE not being the cause, I'll try to sort out the CEL, then attack the DPFE. Thanks again.

To adsm08,
I'm attempting to attach a table that outlines real time monitoring data that I saw when running at the engine under different conditions (cold idle, etc). I'll also post the freeze frame data that was associated with two different p0171 codes. Thanks.
View attachment Ford CEL real time data.pdf

 

[JonnyHightower]

Here is freeze frame data from two different p0171 CELs:

Topic First CEL
Fuel system 1 Closed loop
Fuel system 2 Not supported
Throttle position (didn't note)
Load value 54.9%
Coolant temperature 177F
Short term fuel trim 0%
Long term fuel trim 0.7%
Engine RPM 1007
Vehicle speed 4 mph
Intake air flow rate (didn't note)

Topic Second CEL
Throttle position 16%
Load value 48.2%
Coolant temperature 185F
Short term fuel trim 0.7%
Long term fuel trim 5.4%
Engine RPM 1050 rpm
Vehicle speed 2 mph
Intake air flow rate 0.06 lb/min

 

[enjr44]

Read through this threat/post:

http://www.therangerstation.com/forums/showthread.php?t=165693