can be anything possible causes, faulty lamda sensor, airflow meter, wiring, ecu fault, air leak, faulty injector list goes on.....

this is why as someone already suggested getting it checked out by a diagnostic machine should read any faults and narrows the problem down.

170 miles to a tank is really bad.

surely it must feel slow or crappy to drive, does your car feel lumpy on the throttle, and does it hesitate on the throttle?