Any Ideas, I had a tech II scan ran and everything was clear, no codes in any modules. I have driven about 100 miles and used a half tank. Just normal driving, nothing excessive. Just got the car this week. Is the mileage just this shitty or is something wrong? God I hope this isn't what I have to deal with. I am getting about 14 a gallon.....
Air filter is great, Looks Brand new. The guy I bought it from said it was tuned up recently. It does have all clean and fresh fluids..... I guess I could change the plugs, wires and fuel filter. Any other Ideas?
You said you had a tech 2. Nice. When you ran the scan did you notice if the O2 mV'* were toggling fast from 100'* to 800'*? That is how you tell if the O2 sensor is good. Your O2 controls most of the fueling/richness issues when the rest of the car appears to run properly. After that the next biggest item would be a dirty MAF sensor.
Old O2 sensor, dirty MAF, worn out plugs, old plug wires, weak coils, heavy foot. All of these can cause low mileage. Start with a good tune up. Never trust the last owner. Always new fluids and full tune up.
If an o2 was bad would there be a code? I am used to working on Audis and VW'* and they will have a code and basically tell you exactly what'* up. My coworkers brother is a tech at a gm dealer and he brought the tech II to our shop yesterday. Everything was good except for something to do with onstar.
I would start looking where Bill and Dan suggested. However, I had a coolant temp sensor fail which resulted in horrible milage. Check the coolant temp with the Tech II and see what it reads....if it shows a very low temp, the pcm will think that it is cold and adjust to a very rich mixture. If your sensor is totally bad like mine was, your car would run terribly. My PCM thought it was -40 F and really dumped the fuel to her. Perhaps the sensor can degrade partially? Just a thought....good luck