My 2004 Gt 2.0 16 valve has been idling eratically lately. After I start it can go up as High as 2500. Also can give hard start, almost feels like it's either a little flooded or not enough gas. Can't tell which. The Motor Control Failure came on so I reset the ECU to see if it would help. Seemed to help for a couple days then same problems so I took it to read the fault and "table Z50 mixture strength error" came up. Any ideas what this is and how to fix?