Trying to track down lean codes (P0171, P0174) | Ford Explorer Forums - Serious Explorations

  • Register Today It's free!

Trying to track down lean codes (P0171, P0174)


July 1, 2015
Reaction score
City, State
Year, Model & Trim Level
03 Ford Explorer Sport Tr
I have been getting the lean codes for Bank 1 and Bank 2. I clean and replaced MAF. I had previously replaced the famous vacuum elbow (and it's still good). I have had a smoke test done to find any other vacuum leaks. A small amount of smoke came from the EGR, replaced it.

The codes have come back yet again.

I would like to add that the engine occasionally has a bit of problem. When I start it, it may fire up fine, or may want to drop out briefly (or even die). Idle can be mildly rough anytime. I "think" that part may be a fuel delivery issue as it starts via remote (which turns ignition on for a couple seconds before crank), and if I do the same manually, I do not usually have the start issue (but still can have the idle issue). I have recently put injector cleaner in but may not have driven enough yet.

Please let me know what else it may be. I could ask for another smoke test but the EGR was the only leak found.

Thanks for any help.

It could be a fuel delivery issue. I've read where a clogged fuel filter can cause lean codes. You didn't say if you've replaced it. In my experience with Gen II fuel pumps they typically either work (sometimes intermittently) or they don't, but there are sometimes issues with loose/split hoses lines inside the fuel tank. Although rare, the fuel pressure regulator, which is part of the fuel pump assembly, can sometimes crack. IDK about the '03 models.

The best thing to do is to measure the fuel pressure at the fuel rail. My 2000's and 2001's should read around 65-67 PSI at the fuel rail. IDK if an 2003 should be the same. If you haven't replaced the fuel filter in a while (Ford recommends replacing them at 30,000 mile intervals) I'd start there.

I have not replaced it in a long time. I will try that next.

I certainly hope it's not a fuel pump issue.

When you get the old fuel filter off, try blowing through it, first from tank side and then from the engine side. I've replaced filters where you couldn't get any air through them from the tank side and when you blow from the engine side it's pretty typical to have light brown coffee w/cream-looking goop comes out. Blowing on a new filter is very easy to do.