Mileage drop after replacing sensor........

[Mohycle]

I have a 2003 non turbo 5 speed, 69,000 miles. Just replaced cam position sensor after getting code 0344. Now will run over 2500 rpm ok and no trouble codes. But my mileage has gone from around 25 mpg to about 12 mpg or so. Runs rough. Plugs and wires and air filter were upgraded about 6k miles ago. This drop was very sudden, right after the sensor replacement. I assume something did not reset. Is it fuel mixture/timing/computer/crank sensor/o2 sensor....?????
I did not disconnect the battery when replacing sensor. Will try that tonight. Any other suggestions?
Thanks!
Mo

[CREWZIN]

25 down to 12 ???? I've never read in any of the forums a drastic drop like that. Keep the negative cable off for at least 5 minutes, hope that helps.

Did you mess around with the 'target magnet" where the sensor was. There's locating holes and dowels that place the magnet together in a particular place if you did remove the magnet.

[Mohycle]

Thanks Crewzin,
I disconnected the negative for a couple hours, and also disconnected the sensor. Reconnected the sensor, reconnected the battery, now after a half tank, seems to be back to 25 mpg or so. I may have exaggerated the initial mpg drop; pilot error. My tank was not topped off before. But there definitely was a drop, which now is better.

Thanks again. These cars are a little high maintenance, and the info on this site has saved me lots of time, trouble, and money.

Mo