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Emissions Test Failure


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Corsaman
New User

Jul 26, 2018, 2:25 AM

Post #1 of 4 (148 views)
Emissions Test Failure Sign In

Hi - my Vauxhall/Opel Corsa has failed the emissions test due to high emissions!

This car passed the test with flying colours in 2017, but about 6 months ago was intermittently giving DTC codes relating to O2 sensor, lean mixture, lean mixture at idle, etc....

Changed the o2 sensor, but faults returned intermittently.

On the advice of a local mechanic, I cleaned the intake manifold and throttle body, and cleared the codes.

The car now runs fine, but when the emissions were tested, they were out by a mile! - e.g. CO TEN TIMES the limit, HC, 50ppm over the limit!

I have been going through the sensors. The Air Intake sensor is OK (resitance changes significantly with temperature), the MAP sensor (it doesn't have a MAF sensor) is OK (1.1V at idle, 3.9V when revved), The top O2 sensor has been changed twice now, once by me and once by a local garage. I have now refitted the original one, after testing it with a blow-lamp

Any ideas what I should check next? I haven't checked bottom O2 sensor, or coolant temperature sensor, but would these have such a significant effect?

What can be causing such a massive increase in emissions?

Thanks in advance for your help!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 26, 2018, 3:54 AM

Post #2 of 4 (132 views)
Re: Emissions Test Failure Sign In

Let me start off saying that we don't have that vehicle here in the US so we don't have anything vehicle specific for info.


Quote
I have now refitted the original one, after testing it with a blow-lamp


I have no idea what that is but I am not aware of any way to test an 0/2 out of the car.

It's pretty easy to test in the car though.

You really need a good scan tool to go through the sensor data to see what each sensor is reporting.
Yes, a temp sensor or the actual temp of the engine can have a big effect on emissions.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Corsaman
New User

Jul 26, 2018, 9:43 AM

Post #3 of 4 (113 views)
Re: Emissions Test Failure Sign In

Thanks for the reply. A Vauxhall Corsa is a small car with (in my case) a 1.4L Petrol Engine I posted it here as the general principles are the same for any modern car with lots of sensors and engine management....

You can test an O2 sensor by measuring the resistance of the heater circuit with a meter. You can also measure the signal output whilst heating the sensor with a gas torch and measuring the resistance change.
The scan tool is a good idea. Can you recommend a cheap one? I have a very cheap one, which (as far as I know) can only read DTC codes - not live data. Live data would be useful!


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jul 26, 2018, 12:47 PM

Post #4 of 4 (106 views)
Re: Emissions Test Failure Sign In

I know you can test the heater circuit but you can't know how sensitive the sensor is and how quickly it responds unless it is in a car under controlled situations.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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