we have a 2000 zafira 1.8 16v ,it has the engine light on and will only run if you hold the throttle down ,and even then it has a missfire ,the plugs are new ,but are very black ,i have tried a obd2 code reader on it ,didnt work ,has anyone had this before and how did you fix it ,i am waiting for a tech2 reader to come (ebay) ,