well my car misfired once on Thursday and the next day (after only changing the oil and valve cover gasket) the car started but was repeatedly misfiring. we started replacing things as the codes popped up. spark plugs and wires, o2 sensor, cam shaft sensor and then crank shaft position sensor. after the spark plugs the car only started off and on. and now wont run at all. we had the last part put in at a reputable shop. this mechanic spent 10 hrs working and researching this and cant figure out what is wrong. this is the only car that has EVER left his shop not running an dhe has been there for over 20 yrs. any suggestions??