O2 sensors very low readings

2002 MAZDA MPV
95,000 MILES
Avatar
CIPI64
  • MEMBER
  • 1 POST
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.

Jul 11, 2012 at 5:50 PM
Advertisement
Avatar
DOCFIXIT
  • ASE Certified Mechanic
  • 18,828 POSTS
  • ASE Certified Mechanic
Exhaust leak before O2 and CAT will dilute exhaust gas so O2 voltage will be low cause mix is lean.
Jul 11, 2012 at 5:58 PM
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.
Ask a Free Question
Repair Safety Notice: This information is for general instructional purposes only. Vehicle repair can be dangerous. Verify all information, follow manufacturer service procedures, use proper tools and safety equipment, and consult a qualified repair shop when needed.