o2 sensor problem?

[nope-mx3]

Just got back from a test on my car.
Seems the CO levels are way to high, should be below 0.5, mine was 2.29.

I replaced the cat 1.5 years ago, so I don`t think that`s the problem.

My guess is the o2 sensors, that they are not working, og giving totally wrong numbers to the ecu.
When he pushed the throttle, and kept it for 2-3 seconds, the CO levels increased very fast.
They kept rising until he released the throttle.

Isn`t this a classic o2 sensor problem?
Also, I see I can use some Bosch universal O2 sensors, but is there no any non-oem that fits without splicing or soldering?

nope-mx3

[nope-mx3]

also, is the two o2 sensors on the Mx3 identical?

nope-mx3

[MarkMoore]

Actually, i have no idea how to answer your answer but i also need to replace one of my O2 sensors. I talked to a mechanic friend of mine and he told me that there were actually 4 different O2 sensors in the mx-3. i was always told there were only 2 though. How difficult is it to replace one of these bad boys, and w/o diagnostic equipment, is there any way to determine which sensor it is?

[MarkMoore]

WOW, answer your QUESTION

[IanL]

The majority of MX-3 V6s have two O2 sensors, which are different. I don't know what the difference is, but it could just be the length of the cable.

'96 model MX-3 V6s sold in Canada are OBDII, and have four O2 sensors. I have no information on types, because my parts list is UK, and our cars did not get OBDII.

A rough sensor test is to disconnect the sensor and put a voltmeter between A and B terminals (Left side Red/Blue and Black/Brown, Right side White and Black/Brown).

Warm the engine at 4,500 rpm until voltmeter reads 0.7 V. Then decrease and increase engine speed several times. Decelerating, the reading should drop below 0.4 V, accelerating it should be above 0.5 V.

Mazda dealers have a special test set, which enables them to determine which sensor has a defect. It plugs into the diag connector, and, with the test set set to O2 test, you get 10 flashes if the left sensor is good, then you hold the brake pedal down and repeat for the right. It looks like the ECU is running a self test routine, but to do it without the test set, you need to know how the test set tells the ECU to run the test, and which monitor line carries the flashing.

[nope-mx3]

I measured my sensors on the car, and on idle one was static at 0.9v and the other was static at 0.8v.
CO levels was between 3 and 4 (should be below 0.5).

When we increased the rpm, the sensors started to vary and the CO levels dropped to below 0.5.

Now I start to wonder what the problem is, shouldn`t the sensors vary when idle aswell?
Seems to run very rich at idle.

I talked to Mazda, and they said it might be my oil that needs to be changed... I got 4 quarts of Redline, a can of engine flush, and a new filter.

Would be nice if the oil is the problem.

nope-mx3

[lakersfan1]

Originally posted by nope-mx3:
I measured my sensors on the car, and on idle one was static at 0.9v and the other was static at 0.8v.
CO levels was between 3 and 4 (should be below 0.5).

When we increased the rpm, the sensors started to vary and the CO levels dropped to below 0.5.

Now I start to wonder what the problem is, shouldn`t the sensors vary when idle aswell?
Seems to run very rich at idle.

I talked to Mazda, and they said it might be my oil that needs to be changed... I got 4 quarts of Redline, a can of engine flush, and a new filter.

Would be nice if the oil is the problem.

nope-mx3

They should vary at idle too. I have no idea WTF new oil would do for your O2 sensors. If I had to guess, I'd say your O2 sensors' heating elements are either bad, or the circuit on the wire side for the heaters is bad somewhere.

[93mx3v6]

if the model has 2 o2 sensors they are mass air flow sensor and regular o2/co2 sensor.. mass air flow is located in the air intake hose, (between your airbox and intake) there is a wire plugged into it. its fairly big, the other one... i dunno. but im guessing you wont have to worry about that one. that dosent sound like your problem

[johnnyb]

the 2 o2 sensors in the car are the exact same. The only reason for mazda to have different part numbers is because if the wire length but if you go buy aftermarket universals they'll give you 2 of the same thing then the hardest part is taking them out.

[IanL]

Originally posted by 93mx3v6:
if the model has 2 o2 sensors they are mass air flow sensor and regular o2/co2 sensor.. mass air flow is located in the air intake hose, (between your airbox and intake) there is a wire plugged into it. its fairly big, the other one... i dunno. but im guessing you wont have to worry about that one. that dosent sound like your problem

There ARE two O2 sensors, one in the left bank exhaust, and one in the right bank exhaust.

The V6 does not have a Mass Airflow sensor, it has a Volume Airflow sensor.

[nope-mx3]

I`ve bought two used o2 sensors from Pat, hopefully they will get me through my MOT.
Any tips on what might be wrong if they dont cure the high CO levels? (given that they actually do work). Swapped my cat 1.5 years ago, so I don`t think thats the problem atleast.

nope-mx3