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hey im trying to help a friend and dont have much time for serching can anyone help me and tell me what a p0171 and p0172 error codes tripping the check engine light would or might be. the truck is all stock. its a 1997 ford expo
I don't have a 5.4l Triton motor so I can't tell you from memory; however, on the driver's side cam cover, back under the firewall, you should FEEL (you won't be able to see it) a rubber elbow going into the cam cover. This is likely cracked or broken and is the cause of the vacuum leak, which is causing the lean codes on banks 1 & 2.
If I didn't get the exact location correct (perhpas one of our other members can be more specific) it IS a line leading off one of the two cam covers. Like I said, you should be able to feel your way around.