Quote:
Originally Posted by Old Mechanic
It's been my experience that oxygen sensors get "lazy" as they age. They finally get so slow at responding that you get a CEL. I had one go bad in my 02 Insight at 40k miles, but I think it was from oil contamination from the previous owners addition of a K&N air filter which was soaked in oil.
regards
Mech
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Since you have a lot of experience with cars, I thought I might run my theory with you... If you have a lazy O2 sensor but a clean MAF, that helps a lot doesn't it? My MAF was dirty AND I have 12 year, 140000 mile old sensors, and first tank I got 22 mpg average (with some parking lot start practicing), but I just remember the engine being extremely weird at lower rpms (where I like to drive). Well turns out the MAF was covered in a nice thick layer of black stuff, and as soon as it was cleaned it was 10 times harder to stall the engine from a stop. Just like that, I went from stalling out at lights up to 3 times to never stalling again pretty much. The next tank I had probably wasted just as much fuel doing a "steam clean" as I had on the previous tank in the parking lot, but I got 27 mpg instead of 22.
It would seem to make sense since the MAF reading is essentially the first determinant of fuel injected quantity, and the O2 sensor is double checking, so even if the O2 sensor is old, if the MAF is responding well then the fuel trim shouldn't vary as much right? (that doesn't mean the O2 sensor is giving the correct value of course, and my car still stinks...will change the sensors in a few days).
As far as sensor life goes, my mom's Honda Pilot has a bit under 110k, never changed O2 sensors, exhaust smells like roses compared to my car. It seems to burn a small amount of oil but nothing notable. My car has an early 1ZZ which is known for burning oil in huge quantities. I looked through the previous owner's maintanence logs, and discovered the engine had been burning oil for some time, smog results from the past few years have been pass but way more pollutant than average, and most importantly, the post-cat O2 sensor had died under 2 years ago. The post cat O2 sensor died again just a few weeks after I got the car...
Seems like O2 sensors really hate burned oil.