I have a 99 GMC Sierra. I ran two codes that are PO171 and PO174 which say
the car is too lean. What should I look at to see why it is lean? The car
ran real bad but began to run better. It still misses once in awhile but
still shows the two codes.

On Sat, 18 Feb 2006 22:05:30 -0500, "lukeluke" <lukascj@yahoo.com>
wrote:

>I have a 99 GMC Sierra. I ran two codes that are PO171 and PO174 which say
>the car is too lean. What should I look at to see why it is lean? The car
>ran real bad but began to run better. It still misses once in awhile but
>still shows the two codes.

Check fuel pressure and fuel filter for starters