is my lambda sensor faulty

[Mark c]

hi, need some help diagnosing if i have a faulty o2 sensor. any garage i spoke to just want to through sensors at it till its fixed, they arnt paying for it though. symptoms are, alot of black smoke when accelerating, mpg dropped 10, no fault codes, regenerating the dpf alot, hesitant, misfire when idle. lambda ratio minus 0.5 to o.8, lambda voltage bottoms out at 0.01 volts on my obdll reader, maf sensor reads from 10g/s to 170 g/s. anyone else seen symptoms like this so i can change the actually faulty sensor and not guess work. pic attached showing lambda voltage dipping. thanks people😀

[Shahpor]

Hello,

I am actually not sure what the figures are supposed to be, but the manual states the following:

 

Apparently, testing the MAF is a bit more tricky.  You need to follow this procedure:

Less than 0.36 g/sec. (+/- 15%)

If the result is not as specified, replace the MAF meter.

 

1. Start the engine and warm it up with all accessory switches OFF (until the engine coolant temperature is 75°C (167°F) or more).

2. Drive the vehicle at 50 km/h (31 mph) or more for 3 to 5 minutes (*1).

3. Allow the engine to idle for 2 minutes (*2).

4. Perform steps (*1) and (*2) at least 3 times.

5. Turn the engine switch on (ACC).

6. Turn the engine switch on (IG) (do not run the engine).

7. Turn the tester ON.

8. Select the following menu items: DIAGNOSIS / ENHANCED OBD II / DATA LIST / PRIMARY / MAF.

9. Wait 30 seconds, and read the values on the intelligent tester.

   Standard condition:

Not sure if this is of any help, but I am not sure what else to suggest I am afraid.