What can make my gas mileage suffer so bad that it has fallen from 30-33mpg to 26-28mpg? On top of that, power is down. No check engine light is coming on...would it help to bring it to Nissan and have them diagnose it?
I'm having the same problem with my 1990 Stanza XE engine runs fine but gets really crappy mileage and NOT blowing black smoke indicating a very rich mixture. There is black soot in the end of the muffler so i know its running somewhat rich. Would changing the O2 sensor or as the manual calls it the exhust gas sensor?