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Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - RobWai

Hello all,

Hoping for a bit of help here - never had to diagnose emissions problems before.

The Micra is a 2001 K11 1.0 coilpack version. Had it tested at two different garages with the following results (permitted ranges in brackets)

GARAGE 1

Fast idle CO - 0.06 (0.20) PASS

Fast idle HC - 20 (200) PASS

Fast idle Lambda - 1.014 (0.970 - 1.030) PASS

Natural idle - 1.36 (0.30) FAIL

GARAGE 2

Fast idle CO - 0.063 (0.200) PASS

Fast idle HC - 50 (200) PASS

Fast idle Lambda - 1.004 (0.970 - 1.030) PASS

Natural idle - 5.430 (0.300) FAIL

Between the two tests I tried a few things including cleaning the idle control valve, Italian tune-up, new plugs, etc, but the second set of results are worse. The first garage wanted to replace both O2 sensors and the catalytic convertor, but at a cost more than the car's worth!

Note at no point did the engine management light come on (apart from for 1 minute after I first drove with the new spark plugs in).

I got an OBD scanner (OBDLink SX to link to a laptop) which gave only one fault for STORED fault codes - P0120, indicating an incorrect voltage from the Throttle Position Sensor. However, on clearing the code and running the engine again, I couldn't get the code to come back again. On checking the resistance on the TPS with the sensor disconnected I'm getting 2Kohm regardless of accelerator pedal position. But no further fault code.

As the emissions are fine on the fast idle, I'm inclined to disregard the suggestion to replace O2 sensors and catalytic convertor and concentrate on the TPS and/or throttle body. Right or wrong?

Advice, please!

Regards,Rob

Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - elekie&a/c doctor

Firstly,as I always say,you can't fix cars on fault codes alone.Unlikely to be tps or throttle body.What are the Maf and lambda sensor voltages at idle?

Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - focussed

Firstly,as I always say,you can't fix cars on fault codes alone.Unlikely to be tps or throttle body.What are the Maf and lambda sensor voltages at idle?

Errr- sorry to but in here Doc but there was a problem with K11 throttle bodies.

Wasn't it something to do with the TPS output?

www.ecutesting.com/nissan_micra_stalling_eratick_....l

Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - elekie&a/c doctor

Not on the models with coil over plug systems.Throttle body issues are on those engines with a dizzy and leads.

Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - RobWai

For the two O2 sensors, the voltages at idle (1000rpm, unlike at the Mot where it was 600rpm) are 0.8v and 0.9v respectively. Can't check the MAF tonight, so may need to try that one tomorrow.

Aye, this is a coilpack version with the Bosch throttle body. Worth checking any difference with the MAF disconnected anyway?

Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - elekie&a/c doctor

Something not right here .The upsteam sensor (top sensor should be fluctuating between around 0.2-0.8 volts and the downstream (lower) sensor should be static at around 0.4 -0.6 volts.

Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - RobWai

Something not right here .The upsteam sensor (top sensor should be fluctuating between around 0.2-0.8 volts and the downstream (lower) sensor should be static at around 0.4 -0.6 volts.

I've seen 0.2-0.8v on the upstream sensor at 3000rpm, but not at idle. Will recheck tomorrow. Ta for the pointer as to what I should expect.

Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - Railroad.
Personally I would buy a bottle of injector cleaner and give the car a good hard run. You may be amazed at what difference it could make. Partially blocked injectors with erratic spray patterns won't do much for combustion efficiency. In a worst case it'll make no difference. It definitely won't make anything any worse.
Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - RobWai

Thanks for the replies. Think I may have fixed it, though I'll only know for sure when I go for retest.

Doc - On looking at ODBWiz graph showing O2 sensor voltage fluctuations, with a properly warm engine at 3000rpm the upstream O2 sensor was reading 0.2v - 08.v, while the downstream was reading 0.7v -0.8v. The downstream sensor voltage is higher than what you quoted, but I'm not worried there, as the car DID pass the fast idle test at this RPM.

But at idle (640rpm) I was getting steady 0.8v and 0.9v on the upstream and downstream sensors respectively. So fuelling as if the engine was cold?

Then I tried swapping the throttle body with one from the scrappy. Looks like Focussed was onto something, for after the swap I was getting the expected voltage fluctuations at idle (640rpm) - 0.2v - 0.8v on the upstream sensor, approx 0.8v steady on the downstream. A revving problem was fixed too.


Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - elekie&a/c doctor
By swapping the throttle body,you have also changed the maf sensor .this would account for your emissions and revving problem.Early micro k11 models run a completely different injection system with a different throttle body,that are a common issue.
Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - RobWai
By swapping the throttle body,you have also changed the maf sensor .this would account for your emissions and revving problem.Early micro k11 models run a completely different injection system with a different throttle body,that are a common issue.

Aye, I know the MAF sensors on the later K11's are meant to be better, but I have seen forum posts with people having grief with these too.

Think I will go for the retest. It'll be a while before I get a chance to take it in, but I'll report back on the result

Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - Railroad.
I wouldn't get too excited. The output voltage from the O2 sensor after the catalyst is for reference only. It merely tells the ECM that the catalyst has done its job, or not as the case may be. The ECM does not respond to to the information received from it like it does from the pre-cat sensor.
Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - RobWai
I wouldn't get too excited. The output voltage from the O2 sensor after the catalyst is for reference only. It merely tells the ECM that the catalyst has done its job, or not as the case may be. The ECM does not respond to to the information received from it like it does from the pre-cat sensor.

The interesting bit wasn't what the post-cat sensor was doing, it was the voltage fluctuations on the upstream (pre-cat) sensor.

Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - RobWai

Got the Mot done - PASS, no work required at all!

Thanks all


Nissan Micra K11 2001 coilpack - Failed Mot on emissions - natural idle CO only. - Fiesta-Ranger

I had similar problem, passed MOT for 3 years and garage was aware of emissions problem. Year 4, my luck ran out. Catalytic converter had to be replaced.

 

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