Hazim ... 3/4/2011
1990 Ford LTD Crown Victoria Base 8 Cyl 5.0L
Car using too much gas scanner result codes 91
replaced oxegen sensors got code 91-Exhaust gas oxygen (EGO) sensor -signal voltage always indicates "lean" either during Engine Run Self Test (rich air/fuel conditions)or normal engine operating conditions
Try to navigate this link http://www.extreme-check-engine-light-codes.com... to have an idea how to extract stored trouble code in your vehicle with out using a scan tool to verify if you can it still 91 trouble code.