High CO Emissions
Discussion
Hi All,
My Yaris has just gone over the CO limit on the MOT emissions test. Everything else is normal HC, Lambda etc.
The code P0172 is also showing which is "System Too Rich".
The car is 19 years old and when it's first started I can smell petrol outside and sometimes when I get out after driving it I can smell it too. I've tried Cataclean and i've also cleaned the MAF.
I'm thinking it's the CAT? Any thoughts?
Ross.
My Yaris has just gone over the CO limit on the MOT emissions test. Everything else is normal HC, Lambda etc.
The code P0172 is also showing which is "System Too Rich".
The car is 19 years old and when it's first started I can smell petrol outside and sometimes when I get out after driving it I can smell it too. I've tried Cataclean and i've also cleaned the MAF.
I'm thinking it's the CAT? Any thoughts?
Ross.
stevieturbo said:
Check the lambda sensor is working correctly, although that really is barely a fail at all.....tester needs a slap. Was everything up to operating temperature ok and taken for a drive immediately prior to the test ?
Yes it was up to operating temperature and driven beforehand. Not sure how I test the lambda sensor? The pre-cat sensor is only 2 years old.
rossh123 said:
Sardonicus said:
Do you have a post cat 02 sensor? whats its doing is it switching? that code is a system rich not a catalyst efficiency fault code/DTC if indeed you have a post cat 02 sensor 
what vehicle ?
Yes it has a post-cat O2 sensor, it's a Yaris 1999 1.0L. what vehicle ? without this its hard to confirm E-bmw said:
Mignon said:
CO is very slightly rich but lambda is not which says there must be oxygen in the exhaust system compensating for the CO reading. Check for exhaust leaks, especially at the manifold end.
^^^^Wot 'e said!
and the tubular exhaust manifolds of this engine are prone to perforate on the primaries where they meet the head flanges old age etc, I have changed a few over the years the blow starts off small so often goes undetected until a DTC pops up but by this time leaking is obvious If the whole emissions system is working, you should see the lambda sensor output cycling between 'rich' and 'lean' signals every few seconds.
How those signals appear on a meter will depend on the sensor type but you should see the voltage on the signal line swing pretty clearly.
If one of the sensors is dirty, the system may cycle slower.
If there's a fault anywhere, it will probably be pegged rich or lean. That doesn't necessarily mean the sensor itself has failed - the fault could be elsewhere.
How those signals appear on a meter will depend on the sensor type but you should see the voltage on the signal line swing pretty clearly.
If one of the sensors is dirty, the system may cycle slower.
If there's a fault anywhere, it will probably be pegged rich or lean. That doesn't necessarily mean the sensor itself has failed - the fault could be elsewhere.
Sardonicus said:
ctually reading this post again I also agree and the tubular exhaust manifolds of this engine are prone to perforate on the primaries where they meet the head flanges old age etc, I have changed a few over the years the blow starts off small so often goes undetected until a DTC pops up but by this time leaking is obvious
I will check for exhaust leaks upstream of the cat. The manifold has recently been replaced so I doubt it's that. and the tubular exhaust manifolds of this engine are prone to perforate on the primaries where they meet the head flanges old age etc, I have changed a few over the years the blow starts off small so often goes undetected until a DTC pops up but by this time leaking is obvious Gassing Station | Engines & Drivetrain | Top of Page | What's New | My Stuff