I have a 2000 F150 2 wheel drive extended cab. 6 cylinder motor with approx 90000 miles on it. The check engine light is on. I borrowed a code reader and get 2 codes P0171 (System too lean "bank 1) and P0174 (System too lean "bank 2).

Gos mileage has dropped significantly, truck doesnt idle well, surges on idle to the point you have to take it out of gear at red lights, and the air conditioner sometimes blows out the defrost vents usually when you push down the gas to go uphill. Truck seems to run fine out over the road except for poor fuel economy. I haven't checked it in a while, but gas mileage used to be very high teens or lower 20's on the road.

I suspected a vacuum leak, but can't seem to find any hoses bad. I am not very mechanically inclined. Any ideas on what's wrong or where to start troubleshooting.

Thanks for the help

 

One thing I forgot, the ABS light is on.

 

I had the same codes when I had a vacuum leak. My ac did the same as yours too I found my leak behind the battery where the lines go into the firewall. There are several lines behind the battery & a one way valve that can leak too. I hope this helps.

 

a simple way to fine a vacum leak is to spry carb cleaner around and along the hoses, spray and stop and listen when the engine idles raises or races and then goes back down that is the area of the vaccum leak. dont know about the defroster problem.

But when my truck received the two codes you received I replaced both the upstream O2 sensors and it fixed the problem. the O2 sensors usually go out around 100,000 miles.
My two cents

Lance

 

I will check those places.. Thanks for all the help

 

i had the same thing with my 2000 f150 4.6. you have to replace the fuel filter. i also cleaned my mas air sensor.