Emissions failure

[Barry Gadd]

Just took the Z3 to the MOT centre for an emissions check before going for a new MOT.
I haven't rushed out to buy a new cat + Lambda sensor as I have to watch the cash flow.
The car failed.
So far I've:-
1) Measured the oxygen sensor output and it cycles between around 0.1v and 0.8v (measured with a digital testmeter)
2) Checked the sensor heater resistance (measures approx 3 or 4 ohms)
So I'm inclined to believe the sensor is ok.

I saw on internet a post where the guy advised the cat OUTLET temp is several degrees hotter than the INLET temp.
I tried measuring these temps with a thermocouple contact probe and although I doubt my measurements are accurate I'm pretty sure my inlet temp is higher than the outlet.....

Does anyone know about this cat test or any other that will indicate if it's working properly?

Lastly, is there a fuze or relay in the lambda sensor heater connection? My engine is the 1.9L M44 B19 and I can't specifically find either in the info I have here.
Sorry to keep asking questions but I'm determined to get the car MOT'd
Thanks

 

[t-tony]

What were the readings Barry?

 

[oldcarman]

Barry, you can't get answers if you don't ask all those questions. Use the knowledge these people have to offer up freely and enjoy the learning process. You're going about this the right way, test, post results and wait for those who know to interpret. Keep at it fella, it's come a long way!! JIM

 

[Barry Gadd]

Hi t-tony
The tester didn't give the actual values of the emission failure but this is the second time it's failed.
I've got to know the MOT manager reasonably well and it was he who agreed for me to take the car back for the emissions check.
What I'd like to do is check any fuze or relay in the oxygen sensor heater circuit to see if the heater is actually working.
I did unscrew the sensor and then switch the ignition on to see if the sensor would get hot. It didn't but I'm not sure how the engine ECU earths the heater line to make the circuit.
So it maybe that the heater will only heat up with the engine running.
Any ideas??

 

[t-tony]

It would be easier to advise if you had a print out of the results Barry. Also did he measure the oil temperature?

 

[oldcarman]

Hi Barry, I've noticed from previous posts that most members give the car a hard run for 1/2 hr and then get the emissions test done as soon as possible which seems to make sense as the oil is hottest as are all of the exhaust pieces involved. Am I correct here T-?

 

[t-tony]

You are Jim, but the reason I advocate measuring the oil temperature,which they should anyway, is that you are then testing the emissions at a known temperature. Which means if you carry out any repairs and/or adjustments it is then easy to test again at that known temperature, then it's easier to tell if you have many any improvements or not.
I hope that makes sense.

 

[Barry Gadd]

I did take the car for a run before going to the test centre and they did put it on the emissions test fairly quickly and rev the car for a few minutes before testing.
They didn't measure the oil temp.and I confess,I didn't ask them to do this.
I'm going to get the car up on blocks today,run the engine with a couple of probes (pins) inserted into the oxygen sensor heater connections and see if 12v does appear across the heater element with the engine running.
One question:-
If the heater doesn't function, will the oxygen sensor work or give an erroneous reading? Does anyone have experience of this?
Thanks.