Failed MoT on emissions
Discussion
As title - failed this morning. On the advice of the garage dropped a bottle of Forte Gas Treatment in the tank and went for a hoon, re-tested with everything red-hot... still failed.
One or other of the CO and Lambda values failed over several attempts at the Fast Idle tests.
E.g. Fast idle test
CO Max 0.3%, measured 0.00% PASS
Lambda 0.95-1.03, measured 1.10 FAIL
Second fast idle test
CO Max 0.3%, measured 1.60% FAIL
Lambda 0.95-1.03, measured 1.02 PASS
Garage are not a Noble specialists but did what they could... their emissions testing machine didn't list any Nobles so they put it in as a Ford Maverick (3L V6).
Mole Valley are my nearest dealers so guess I'll run it up there for a diagnostic check, unless anyone knows a suitably equipped independent in either Sussex or Kent?
Realise it's not a lot to go on but is there any easy way to tell if the lambda sensors and / or the cats are faulty? And if they are, what sort of cost am I looking at?
TVMIA, Dave
One or other of the CO and Lambda values failed over several attempts at the Fast Idle tests.
E.g. Fast idle test
CO Max 0.3%, measured 0.00% PASS
Lambda 0.95-1.03, measured 1.10 FAIL
Second fast idle test
CO Max 0.3%, measured 1.60% FAIL
Lambda 0.95-1.03, measured 1.02 PASS
Garage are not a Noble specialists but did what they could... their emissions testing machine didn't list any Nobles so they put it in as a Ford Maverick (3L V6).
Mole Valley are my nearest dealers so guess I'll run it up there for a diagnostic check, unless anyone knows a suitably equipped independent in either Sussex or Kent?
Realise it's not a lot to go on but is there any easy way to tell if the lambda sensors and / or the cats are faulty? And if they are, what sort of cost am I looking at?
TVMIA, Dave
Hi Dave mine failed on emissions yesterday too 
FAST IDLE LIMIT
lamda 1.04 0.97-1.03
second test gave the same readings
I had a feeling mine might fail as i have a cracked manifold and the rest of the exhaust is blowing from every gasket
New exhaust and welding of manifold will be happening next week
FAST IDLE LIMIT
lamda 1.04 0.97-1.03
second test gave the same readings
I had a feeling mine might fail as i have a cracked manifold and the rest of the exhaust is blowing from every gasket
New exhaust and welding of manifold will be happening next week
Dave2P,
You almost certainly have a leaking exhaust system and possibly manifold (excess air causing a lean lambda reading) - if the lambda (HEGO) sensor sees the air, it richens up the fuelling and causes a high CO reading. If it doesn't see the air in the exhaust, then the CO is right but the lambda value comes out lean (i.e. greater than 1.03). You have both, depending on how hot the exhaust is, so the air leak is changing.
Oh, and your HEGO sensors could be a bit tired - get a dealer to hook up the diagnostic software and watch for the sensors switching rich and lean - should sweep from 0.1-0.8. If they only get to 0.5-0.6 then they need replacing.
Hope that helps,
YellowShed
You almost certainly have a leaking exhaust system and possibly manifold (excess air causing a lean lambda reading) - if the lambda (HEGO) sensor sees the air, it richens up the fuelling and causes a high CO reading. If it doesn't see the air in the exhaust, then the CO is right but the lambda value comes out lean (i.e. greater than 1.03). You have both, depending on how hot the exhaust is, so the air leak is changing.
Oh, and your HEGO sensors could be a bit tired - get a dealer to hook up the diagnostic software and watch for the sensors switching rich and lean - should sweep from 0.1-0.8. If they only get to 0.5-0.6 then they need replacing.
Hope that helps,
YellowShed
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