I have a 1996 Dodge Neon that used to run really good and get excellent gas mileage. Then one day the check engine light came on and it has lost a lot of power, and runs kind of rough. When I sit a steady 40mph I can feel it kind of sputtering. It is now getting horrible gas mileage and you can smell gas in the exhaust. The engine code it gives me is "P0171 System Too Lean Bank 1". So far I have done a tuneup (spark plugs, wires, air filter, oil change, fuel filter, O2 Sensor). Doesn't run any better.
So I picked up a Chilton Neon Repair Manual, it says you can test the MAP sensor by checking the output voltage with the engine off but key in the on position, and again at a normal idle. It says it should should give 4.5 volts with the key on and engine off, When I tested it I got 15 volts! I didn't know that was even possible as the battery only gives out 12? Then when I start the car I dont think it was giving any voltage or around 1.5. (Did this the other day I forget now, I was testing all the different wires on the sensor. Only the 4th wire is the MAP output voltage. The IAT sensor is combined in it.)
Has anybody else experienced anything similar or know anything I don't or am missing? I figure its probably bad, but it is $85 at Autozone and money is tight, I would hate to replace it and still have the same issues with it.
Thank you for any advice, knowledge, etc. I really appreciate you even reading this.