I have experienced a HUGE mileage drop in my 2003 SXT -- from 30+ mpg to 17 mpg. The manifold vacuum and rpm's seem normal, although the idle is rougher than usual. I installed new plugs and wires not too terribly long ago. It was so fast that I thought it must be leaking fuel somewhere, but it's not. She has about 250K on her. Does anyone have any suggestions? I mean, the mileage has literally been cut in half overnight.

 

Welcome to the 2nd Gen Neon forum. I see you don't have any replies yet, so will see if I can get things started.

Scan the ECM for trouble code clues & post All code Numbers, as they can help focus a trouble shoot. If you don't have a scan tool, or code reader, you can cycle the ignition switch from Off to On (but don't crank the engine) three times, stopping at On the third time & the dash message center will put up stored trouble codes.

 

Well Kurt, how is the trouble shoot going, 191 curious minds would like to know???? If you found any trouble code clues when the ECM was scanned, post them up as they can help focus a trouble shoot.