Mechanics

O2 SENSORS VERY LOW READINGS

2002 Mazda MPV • 95,000 miles

2002 Mazda MPV ES, 3L, 95K

Engine idles rough, but no significant loss of power during driving (though there is some hesitation accelerating).

All 4 HO2 sensors read very low voltages, never more than 0.2V and pretty steady (no oscillation). There are two banks (one for each side of the V6 motor), one upstream of cat and the other one downstream.
There is noticeable exhaust odor near the front of the car, one mechanic sugested that the front exhaust manifold leaks another pointed at two flexible pipes (under the car). Before I put a couple of thousands in exhaust parts I am trying to understand how is it that these readings can be so low on both banks.



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Cipi64
July 11, 2012.



Exhaust leak before O2 and CAT will dilute exhaust gas so O2 voltage will be low cause mix is lean.

Docfixit
Jul 11, 2012.