2008 Toyota RAV4 Q&A
2008 Toyota RAV4 Question: 98 RAV4 runs excellent but throws P0171 code and gets terrible gas mileage. Why?
Just bought and it passed smog easily. No vacuum leaks as far as I can tell. idles smooth and runs great. I realize this is a lean run condition so something is causing it to increase the gas mixture too much. There are so many things to check with a P0171 I don't know where to start. I put fuel cleaner in and it is my first tank. I am actually watching the gas gauge go down as I drive. Air filter is fine. No MAF to clean. Need help please. - bobbuddy
These can be tricky and you have to be careful when evaluating the system. While you say it runs great here I wonder if it would feel the same to a tech. When the system sets a lean (or rich) air fuel code it stops correcting the air/fuel ratio. So if it was out of control to the point that the fuel trim system couldn't correct it, it should run pretty bad when it stops trying. If the system has a defect, for instance a downstream sensor that fails and drops the downstream O2 voltage signal, the system will ignore the upstream sensors information and keep enriching the fuel mixture trying to make that downstream sensor respond. It really will drive the engine over rich, while reporting a lean code but you need a technician who really understands the system to test and prove if that is occurring or not. - cardocIII
could be valve adjustment or have smoke test done to determine vac leak - globalhelper