Morning Guys,
Got a question on my 2000,100000 on the clock,poor milage blazer, MAJOR tune-up done. Clear codes. Anyone know if there could be a bad O2 sensor w/o throughing out a code? 10-11mpg just isn't cutting it !!! The Blazer runs/idles new. Driving it easy too, air pressure ok, stock tires, Any Ideas ?

 

I hate just recommending that someone change out components without properly identifying them as being bad. With O2 sensors, you really need to see the sensor trace, cross counts, and the changes in injector pulse width to know if the sensors are getting lazy. Most O2 sensors fail because they do not report changes in a timely manner, causing the PCM to constantly hunt which wastes fuel.

If you do not have the tools to diagnose them, then your only real choice is to replace and hope that they had something to do with your mileage issues. You only need to replace the two upstream sensors which are the sensors closest to the motor between the exhaust manifolds and the "Y" in the y-pipe.

 

Thanks as always Kyle, just gotta be something, why I'm getting such aweful mileage. If you think of any thing else let me know, Thanks, Nick

 

Are you sure you do not have a brake dragging? It is not uncommon to have a caliper freeze and drag which will kill your gas mileage.

 

That's a good idea, but there definitely not. Thanks