“can the richness be leaned out?”
In a modern car that amounts to fixing the fault that’s causing it to run rich.
Typically a tired O2 sensor.
But you don’t know if that’s the issue with your vehicle.
I too would suspect a possible bad 02 sensor. I’ve seen bad 02 sensors cause as much as 25-35% drop in fuel mileage. Might also be a bad ECT sensor causing the system to stay in open loop too long or all the time, or a brake dragging.
Thanks man. I’ll replace it just to be on the safe side. Is it an easy job to replace it?
What would happen if you just disconnected the O2 sensor? Run rich or lean? Never thought of that before, just wondering. Rocketman
@rocketman, if the O2 sensor was disconnected, the PCM would go into open loop.
Then you’d definitely see lousy fuel economy.
Hey Guys, on my 1991 Jimmy is there more than one (1) o2sensor?