Hi everyone. I have been looking at the board now and then and have always found what I needed to know. Thanks for all the input. I now can’t figure out my problem and am hoping for some insight.
My 98 Ranger XLT, 2.5L, SOHC, (140,000 miles) had DTC’s P0171 and P0174 last summer. The engine was running rough – much like many people have mentioned here: rough on starting but gets better as it warms up. It seemed like it wasn’t getting enough gas. I took the truck off the road for about 6 months after the code came up.
I examined vacuum lines but found nothing. Installed a new EGR and IAC. Replaced the MAF which seemed to help. The fuel pressure was 50 psi so I replaced the fuel pump and filter. Also replaced the pre-cat 02 sensor. No improvement in the rough engine performance but the P0174 code was gone. I also replaced the plugs and wires – it was time to do that anyway. The electrodes on the two under the intake manifold were worn to just nubs. No improvement.
I found the flange between the cat and muffler pipe was leaking and repaired the flange, replaced the gasket. After this the engine would simply stall shortly after starting.
I then found that the PCV valve was not seated in its grommet. The hose was hard and seemed to have pulled the valve up. Replaced the PCV and hose. The engine ran much smoother but the P0171 came on after about a half hour of driving. Replaced the post-cat O2 sensor and cleared the codes. Drove it for about ten minutes and the DTC, P0171: System too Lean, Bank 1 - came back on. (That was fast.) The Load_pct was 60.4; Shortft1 = 12.5%; and, Longft1 = .8%. The OBD monitors for the CAT, EVAP, O2 Sensor Monitor, O2 Sensor Heater, and EGR were incomplete at the time the MIL light went on.
I examined the vacuum hoses and gaskets using propane, again. Found nothing. The crank shaft pulley appears to be 8 degrees BTC when the timing marks are aligned on the cam shaft pulley and accessory. There is also a sound of a valve or pushrod clinking at idle speed. Anyone have any ideas? I appreciate your thoughts. Thanks

 

I found this article regarding trouble code. The DPFE sensor is listed as a potential culprit. Seems like you have covered all the other bases. Check the vac hoses that go to control as well for cracks .

Ford P0171 & P0174 Lean Codes

 

If you have to replace the DPFE here is a link to Rock Auto.

1998 FORD RANGER EGR Pressure Feedback Sensor

 

I had a car do that once. Look at everything finally took it to Cadilliac even thought there where no codes for MAF it turned out to be a combo of air filter and MAF giving computer wrong info running it lean.

 

Thanks for the info. I need to correct - there wasn't a 174 code. It's a four cylinder. Not sure why that was in my notes.

Thanks Maz. I did switch out the DPFE, but did not change the hoses. They looked okay when I pulled the old one. However, considering the condition of the PCV hose, I will change them tomorrow. You have helped me remember that the original codes included the EGR. So I pulled the PDFE as it looked pretty bad. All the repairs have cleared the other original codes except, the 0171 remains.

Thanks as well Taumac. When I first opened the airbox, I found the corner of the filter was torn and bent, leaving a small hole for unfiltered air. I cleaned the MAS and replaced the filter. No help. However, when I unplugged the MAF, the engine ran much better. If I do that now I get a code and it makes the engine run worse. Without finding a vac leak, I am beginning to think this may be the result of false info or maybe the cat.

I'll let you know. Thanks.

 

Didnt mention it but did you look at the injectors themselves. looks like did everything else from fuel tank to fuel rail. Possiblity run some seafoam through tank.

 

Thanks. I did not pull the injectors. I did listen to them with a stethescope. They are all clicking nicely. I am thinkng about pulling the intake manifold and look at the gaskets. I will pull the injectors then but am not sure how to examine them. I am not looking forward to this. LOL. It's about 30 degrees in my garage these days - with my heater running. I have to keep my work time short - them warm up inside.

I did not use Seafoam but did use another fuel line cleaner and Lucas Oil.

 

Hi everyone. Thought I would report in. I was very hopeful today when I found a crack in the bottom of a hose to the DPFE. NO luck. DTC code p0171 came back on after replacing the hoses. However, the OBD monitors for the CAT, EVAP, O2 Sensor Monitor, O2 Sensor Heater, and EGR were all incomplete at the time the MIL light went on. I drove around with the DPFE unplugged (codes cleared) and the DTC light did not come on. as soon as I plugged it in - the P0171 came on. I wonder if the problem is there. I would appreciate your thoughts. Thanks.

 

I did no think those stft and ltft percentages would throw a lean code? you do not have pushrods!

 

Could be those things are PITA. My 92 Ranger didnt have one but Im one 2nd one in my truck in 2 yrs, 1 in sons Mazda , 1 in Expy, 1 im fathers Ranger. They clog easy and there about 50 - 06 buck at parts store. It wouldnt hurt after everything else.

 

I think - hope - I figured it out. Since none of the numbers made sense - and the O2 sensors hadn't competed their monitor test - and I could not find any other leaks - it must be a component or clog in the EGR system. Pulled the EGR presure regulator to test it again. There it was. Replaced it and drove around. The MIL light did not come on. The O2 sensors completed their test. Waiting for the EGR, Catalist and EVAP tests to complete.

Thanks for your thoughts. I would have kept spinning my wheels without.

 

Hi All,

I made some progress. I had some diagnostics done. The mechanic could not find the problem. Everything checked okay. He swapped out the MAF (I purchased at AutoZone) and the fuel system changed dramatically. So I took the part back and got a different one. Truck runs much smoother - but shortly after running the engine, I have a pending P1409. My EGR valve, DPFE and valve control have all been replaced. Maybe I should exchange them all at AutoZone and see what happens. Ha. Thanks for your ideas.

 

I have heard some of the aftermarket replacement parts aren't up to the quality level of the OE parts. Could always try Rock Auto for the Ford parts if you keep getting duds.

 

have you checked the hoses and the metal tube that runs from the egr to the dpfe

 

Both hoses have pressure coming out. I can't find my pressure gauge so not sure how much. It is very gentle.

I back probed both sides of the EGR vaccum solenoid plug and found each has about 3 volts (i think) at idle speed just after starting the engine. No vaccum on the valve though. Applying slight vaccum to the valve causes the engine to sputter and stall - it's good. Haven't checked the Pressure Sensor plug. The mechanic said it was good. Not sure where to look next. I am still thinking about pulling the intake manifold off to peak - clean inside.