Codes 0171 and 0174 Lean

[PaulZ]

Hey guys,

Had both these pop up at different times, lean bank 1 and then bank 2. 1999 Ranger 4.2. Runs fine. Research says fuel pump or filter, vacuum leak, sensor.., Where do I start!

paul

 

[SenorNoob]

If the fuel filter hasn't been changed recently it's probably due anyway. (And fairly cheap) More common however is a vacuum leak. 25 years is about time for factory vacuum lines to have deteriorated to the point that they leak. Best way I know of to check for a vacuum leak is an unlit torch. Move it around the lines with engine running. If the idle changes in a certain spot there is your leak.

 

[PaulZ]

Thanks SenorNoob!

Ok I tried an unlit lp torch with a cold engine and no codes, nothing. Maybe I have to get it warmed up or a code showing.. or maybe propane won’t do it. I even pulled the hose from the valve cover to the air duct just near the Mass Airflow sensor. Idle goes way up unless I put my thumb over the hole. Lp does nothing there either.

im off to buy a fuel filter today. It’s only spit up the code 3 times, and a day or two and 30 miles between.

thanks again, just don’t want to burn a valve or something. You’d never know there was a problem when driving.

paul

 

[SenorNoob]

If the filter doesn't help, next cheapest and simple things to do would be to clean the MAF and or pull spark plugs and check condition.

 

[PaulZ]

Well I tried to pull the filter yesterday (didn’t have new one yet, Napa walking distance). But after finally figuring out those retaining clips I couldn’t yank the hoses off. Turns out there’s a special tool for that?

 

[SenorNoob]

The special tool is for fittings at the engine and maybe fuel pump. The filter is just remove the clips and pull. It may help to get some spray cleaner (carb, brake, doesn't matter) and spray into the connectors. They tend to collect dirt/mud. After you get them as clean as you can, spray with some kind of penetrating oil. Then work the ends loose wiggling and rotating as you go. If the filter is like mine, it's held in by a hose clamp like fitting. Loosen that and turn the filter inside the lines if you can. Be careful not to twist the lines though.

 

[PaulZ]

Ok, I was able to twist the filter around on the hoses, just couldn’t yank them off. Then saw this video of a guy using the tool so I stopped.

 

[PaulZ]

SenorNoob,

Finally some progress! Had a heck of a time with the fuel filter, finally changed it at shop class last night. But the teacher said he doubted that was causing my codes. So he wheeled out his smoke machine, and sure enough found a hardened cracked vacuum hose, way down and in front of the brake master. i can take a photo. He said he was surprised it wasn't throwing some emission code. It did idle a bit smoother after. Today I will clear the codes and see. Also a bit of smoke came out the 'idle speed sensor' thingy up top but not much.