What does running lean on both banks mean on 94 ford mustang?

Answer 1

It could be a couple things. You could have a vaccum leak somewhere. Let the car idle and listen to the motor for any hissing sounds. Often a vaccum leak will be audible. Check all the hoses to make sure they are tight and in good condition. You could also have fuel pressure problems. check vaccum hoses and change fuel filter 1st. If vaccum checks out ok then it may be your fuel pump or pressure regulator. You can go to autozone or advance auto parts to have a scan done. They may tell you if you SES light is not on that it wont give them a code, but have them try it anyways as I had the same situation and it gave 4 codes even though there were no lights on! If its vaccum it should give an insufficient EGR flow code.