97 Grand Marquis OBD Codes

[FakTorThis]

I have a 97 Grand Marquis and the OBD is giving P0171 and P0174 Bank 1 and 2 running lean. It burns gas (http://www.fordforums.com/#) like crazy and my uncle says its running rich and he hopes its not a bad intake gasket the manifold was just replaced because the old one cracked (stupid plastic) so he's hoping it isnt that and he told me to come on here and ask help and what anybody else thinks

[Bradley G]

An intake leak can be the cause of poor mileage.
I did upper & lower intake on my daughters 3.1 Malibu and mileage went up instantly.

[FakTorThis]

I also forgot to mention the major loss of power

[Bradley G]

I was gonna add, besides the 2-3 MPG increase, it feels much peppier.

I also forgot to mention the major loss of power

[carfixer]

Your MAF is dirty. Clean your MAF sensor wire. Very common. Disconnect the battery after or you will have an intermittent stalling concern.

[RF Overlord]

A bad intake gasket is more likely to make the car run lean, not rich, and unless the job was really botched it would not read lean on both banks. I'd look at what carfixer said, or look for another source of a common vacuum leak...PCV sustem, or other vacuum plumbing.