Emissions MOT failure.

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Sarnie109

New Member
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7
Location
Wisbech
Hi Guys. Thought it was time to consult you Oracles again.
'97 4.0 P38 Running sweet as a nut. Fresh petrol, just serviced, new leads, plugs etc.
Under 100,000 miles and it's just failed on CO emissions at 0.338 first idle test and 0.342 second idle test. Everything else passed by very comfortable margin.
I'm at a bit of a loss as I've checked all the usual stuff and not finding any issues. Where am I going wrong guys?
 
Might be worth using a bottle of fuel injector cleaner. Cat converters another possibility. Is the rest of the exhaust system ok?
 
Sarnie109 said:
Hi Guys. Thought it was time to consult you Oracles again.
'97 4.0 P38 Running sweet as a nut. Fresh petrol, just serviced, new leads, plugs etc.
Under 100,000 miles and it's just failed on CO emissions at 0.338 first idle test and 0.342 second idle test. Everything else passed by very comfortable margin.
I'm at a bit of a loss as I've checked all the usual stuff and not finding any issues. Where am I going wrong guys?
Click to expand...

Good long run to really heat up the cats, had same issue on old one with mostly shorter drives never letting the cats regenerate with the needed high long heat.
 
Druim said:
Good long run to really heat up the cats, had same issue on old one with mostly shorter drives never letting the cats regenerate with the needed high long heat.
Click to expand...

Yeah, good point. When mine 'just' failed a couple of years ago, the m.o.t. guys told me to take it for a 5 mile run at high revs. Put it in sport mode (its a 4.6 auto) with plenty of right foot, straight to m.o.t station and it passed. Probably cost me about £50 in petrol but was good fun. ;)
 
Beat me to it guys - I was about to mention the Italian tune-up. Was the car hot enough? Run it at high revs on a fast high road before the test.

I assume you changed the air filter at the recent service too. The #1 reason for petrol cars failing MOT tests on CO2 emissions is the fact they've been driven too gently.
 
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