Hi All,

I recently bought a 97 Ford Ranger 4.0 XLT. Initially i was getting the P1401 code. Other symptoms I was getting were that when it initially started up I would get a strong smell of fuel and it would run for 5 secs then die off and stall. I checked the vacuum pipes (visually) and replaced the DPFE sensor and hoses (one of the hoses just crumbeled as I took it off) which has resolved this issue. No more P1401 code, no stalling and no smell of fuel on start up. So I thought everything was running great until I started getting the P0171 code complaining that "system too lean bank 1".

I searched this and some pointed to the MFA sensor so I took this out and cleaned it with some MFA cleaner but the issue persists. I've narrowed it down to it only happens when the car is idling on an incline such as stopped at traffic lights. It can idle on level ground absolutely fine but every time on an incline after 30 secs the CEL comes on.

Ive read some say the code could be related to the o2 sensor and others who say it's absolutely not the o2 sensor.

my uneducated sense tells me I should look at the fuel pump since it's only on an incline. Am I completely going in the wrong direction? The fuel filter was recently changed.

Any help would be greatly appreciated.