E85 2.0 MOT failure on carbon monoxide emissions

Cv6benplus

Cv6benplus

Member
 Coventry
As per the title and attached image.

1000044211.jpg

I've used cataclean additive in ¼ tank of fuel, taken the car for a decent run, got it very hot and kept the engine hot prior to the emissions test and it still failed and the fuel light was on. It drove absolutely beautifully.

Without opening up a parts cannon, what are the likely places to start looking?

Zero codes on the reader, zero lights on the dashboard.

2.0 55 plate. Prefacelift, digital dipstick.

Thanks for all help.
 
If there’s no codes it implies it’s not a cat sensor issue.
Could well need a new cat.
 
How old is the oil? Whilst this may not be your car's issue, I've seen a Renault fail on emissions and then pass after fresh oil. Never really got up to temperature doing school runs.
 
Some digging needed:

Primary Causes & Faulty Parts:

Catalytic Converter: The converter is designed to oxidize CO into safer CO2 If it is physically degraded or old, it will fail to clean the exhaust, leading directly to high tailpipe CO levels.

Upstream O2 Sensor: If the sensor feeding data to the ECU is failing, it can cause the engine to run constantly rich, outputting more CO than the catalytic converter can handle.

Engine Coolant Temperature (ECT) Sensor: If the ECT sensor reads artificially low (even if the engine is warm), the ECU will inject extra fuel, causing a rich burn and elevated CO emissions.


Secondary Checks:

Mass Airflow (MAF) Sensor: A dirty or failing MAF can miscalculate incoming air, leading to an incorrect fuel ratio.

Engine Air Filter: A heavily restricted air filter starves the engine of air, causing a rich combustion cycle.

Leaking Injectors: A stuck-open fuel injector will dump too much fuel into the cylinder, overwhelming the emissions system.
 
Deepseaskateboard said:
Some digging needed:

Primary Causes & Faulty Parts:

Catalytic Converter: The converter is designed to oxidize CO into safer CO2 If it is physically degraded or old, it will fail to clean the exhaust, leading directly to high tailpipe CO levels.

Upstream O2 Sensor: If the sensor feeding data to the ECU is failing, it can cause the engine to run constantly rich, outputting more CO than the catalytic converter can handle.

Engine Coolant Temperature (ECT) Sensor: If the ECT sensor reads artificially low (even if the engine is warm), the ECU will inject extra fuel, causing a rich burn and elevated CO emissions.


Secondary Checks:

Mass Airflow (MAF) Sensor: A dirty or failing MAF can miscalculate incoming air, leading to an incorrect fuel ratio.

Engine Air Filter: A heavily restricted air filter starves the engine of air, causing a rich combustion cycle.

Leaking Injectors: A stuck-open fuel injector will dump too much fuel into the cylinder, overwhelming the emissions system.
Click to expand...
How many of these would throw up any kind of fault code?
I'm not getting any fault codes.
When being driven or scanned, the vehicle operates as normal.
 
Could be within tolerance.

Aren't cats expensive?

If it’s a couple of sensors could save some cash.
As I said, it needs some digging.

If cats are cheap enough, it’s a decent place to start.
 
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