MOT fail... help please!

[Whiskerz16v]

MOT failed kn a few things but one I'm trying to find problem on is emissions

Failed on lambda and CO reading too high On fast idle

1.14 for lambda ( pass is 0.97-1.03 )
1.95% co ( pass is 0.3%)

Now the exhaust wasn't sealed right just at the join to backbox, but don't think that effects it that much surely?

Ideas

 

[Adam.]

G & M Auto's in Inverkeithing.

Done.

 

[montana]

MOT failed kn a few things but one I'm trying to find problem on is emissions

Failed on lambda and CO reading too high On fast idle

1.14 for lambda ( pass is 0.97-1.03 )
1.95% co ( pass is 0.3%)

Now the exhaust wasn't sealed right just at the join to backbox, but don't think that effects it that much surely?

Ideas

not sure if it would affect it however i wouldnt think you would get it through with a blowing exhaust

 

[Whiskerz16v]

My mates getting parts and sorting it for me, just wasny sure if it's just a faulty lambda sensor or not.

Had a new cat on in October and a centre in December, when it goes up for the retest I'm getting them to put on a backbox for me too.

Getting a new lambda sensor and fitting that going on advice from a few mechanics so fingers crossed that's all it is!

 

[Sborder]

Test the lambda sensor first if you have a tester to do it, if the sensor doesnt solve the problem then chances r it will b your cat mate. lambda readings are basically oxygen so that maybe high from the hole in the exhaust.

 

[MIKE3]

My engine light came on a couple of weeks ago, but the car drove ok. Now I knew the exhaust was blowing a bit from the join between the cat and the silencer. When my mate put the reader on the fault came back as '266 O2 sensor signal before cat intermittant fault' (as well as 301 &309 both brake switch related I think) I fixed the blow on the exhaust thinking it would solve the problem but it hasn't. New front sensor then tomorrow methinks.

 

[Grancio28]

exhaust blows normally just give a high lambda reading e.g 1.030 doesnt normally affect c.o. find some1 with a scan tool and a scope to test sensors. gets pricey just changing things! test the in and out temps of cat before you replace it i use a cheap infrared one of e-bay cost bout £20. did they take an engine temp reading? if the cats not hot enough then it wont do its job.

 

[MIKE3]

My engine light seems to come on when the car is idling just about 30 seconds after turning it on. Wouldn't it smell if the cat was knackered?

 

[Whiskerz16v]

I had a new cat put on in October so I highly doubt the cat is away, getting part fitted tonight then go try book in for retest thurs/fri

Though fo get them to fit a stainless backbox I have at the same time

 

[Martin_172]

sounds possibly like what ever killed your first cat has killed the 2nd.

 

[sideways danny]

the Lambda reading is lean, and an exhaust leak massively effects the reading that the MOT probe sees.

 

[bunzee]

Mine was using a lot of fuel and failing on emissions test, I knew I had one knackered lambda and the car had been running slightly cooler than normal so I had the thermostat, coolant temp sender and both lambdas replaced at the same time as I didn't have the time to be arsing about trying each thing. No idea which sorted it but it's fine now!

 

[Whiskerz16v]

Rust killed the first one lol! Snapped at the join to te centre