I just bought my first car, and it has it's "Check Engine Light" on. After getting a failed emission test, I got a PO171 "Fuel running too lean" code. My car runs terrible Gas Mileage (200 miles full tank) and wanted to know what I could do to make it all better. Granted, it's my first car and I don't know too much about the mechanics of an engine, and I also don't know what many of the parts are. I was just wondering if anyone would take the time to help, or if I would just be shooting in the dart with this new "repair manual" I got.

I have a DOHC 16v 2.0 1997 dodge neon. Just got the timing belt and water pump replaced.

Thank you (anyone) who decides to take the time to help me out.

 

congrats on your first car.
p0171 means that the exhaust stream, as measured by the O2 sensor, is too lean (not enough gas), and that the car's computer has attempted to adjust the fuel mix to its maximum allowed richness (more gas), but still can't get the expected result. so in response to all that, it sets the code and turns on the check engine light, so that you can get it fixed.

the most likely causes of this condition are either a vacuum leak, an intake leak, a clogged fuel filter, or a bad O2 sensor giving a false reading.

was the check engine light on before you had the timing belt and water pump replaced? if not - take it back to the shop and ask them to check for any unconnected hoses, or other problems that might be causing the problem. if it was, and you feel good about the shop, then ask them to diagnose your problem and write up a repair estimate. sometimes the diagnosis is free - but if it takes more than a few minutes to determine the problem - there may be a cost associated with the diagnosis. sometimes the diagnosis cost in included into, or forgiven in the total repair bill.

check for unconnected hoses. its easy for them to come loose, get overlooked, etc.

http://www.obd-codes.com/p0171

 

By checking the hoses, I have made the "check engine light" stay off. However, after noticing last night, my car makes a high frequency sound after I shut off the engine, and step out of the car. It only last for about 10 seconds, but I know it's coming somewhere from my PCM. Any ideas?

 

Air Conditioning pressure bleed off maybe?

 

Heading to work, my check engine light was off. After 5 hours, I turn my car back on and my Check engine light pops on, so I'm back to that.

I'll look into the Air conditioning bleeding, however I manage to do that. I'm looking into the O2 sensor, hoping it would be as simple as that. I know absolutely nothing about cars, except where the parts are located; so that's a plus I guess.