and bad mpg from an o2 sensor is going to be the upstream sensor/sensors.

 

hey Scott-
Thanks for your advice-im afraid I may need some more!!! Had the 02 sensors changed again and then the truck ran fine for about 90 miles or so and then I could smell a slight scent of exhaust and slight vibrating again and then the check engine light came back on and the full on exhaust smell came in and is outside the truck-what else could this be? everytime the mechanic checks on the CEL it comes up with the code for a slow circuit response in the 02 sensors-Im beyond confused at this point-any words of wisdom? Thanks

 

Thanks for your advice-im afraid I may need some more!!! Had the 02 sensors changed again and then the truck ran fine for about 90 miles or so and then I could smell a slight scent of exhaust and slight vibrating again and then the check engine light came back on and the full on exhaust smell came in and is outside the truck-what else could this be? everytime the mechanic checks on the CEL it comes up with the code for a slow circuit response in the 02 sensors-Im beyond confused at this point-any words of wisdom? Thanks