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Discussion Starter · #1 ·
My 2.5 V6 Omega just scraped through its MOT with a high CO figure on the emissions test. The garage was very accomodating and revved the engine to warm up the cats until he got a pass reading!
Does this mean my cats will need replacing before next year? Is there anything else that I should check before going to the expense of changing them?

The car has done 107k miles.

Thanks for any advice.
 

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was this done when cold ?

The V6 lump has a secondary air pump which blows into the exhaust on startup. It's something along the lines of injecting air to help burn the un-ignited fuel prior to it getting to the cats, which in turn helps the cats to warm up.
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Discussion Starter · #4 ·
The car had been driven 1 mile to the MOT station and left idling for 10 minutes prior to the test. The engine was up to operating temperature. Initially the CO level was above the limit of 0.20% and the Lamda reading was also high. After revving the engine the eventual readings were: CO = 0.07%, HCC = 117ppm, Lamda = 1.03.
There are no fault codes on the ECU to indicate a Lamda sensor fault, although the Lamda reading is on the high side. Is there any way of testing them?
 

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i would say that if you gave the car a run out beforehand & gave it a bit of thrash it would be fine , if the lambda reading is high & the co is somewhere near normal this is normally caused by an air leak in the exhaust.
 

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Discussion Starter · #6 ·
Could the secondary air pump be the cause of the problem? If the CATs are cold and the air pump is blowing air into them, would this give the same symptoms as an air leak?
 

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My 2.5 V6 Omega, which I keep in Spain, failed its ITV (Spanish MOT) due to CO = 1.4%. The car often sits in the garage unused for 4/5 months and tends only to be used for short journeys. I took it down the auto pista for 20 miles at 80/90 mph to get the CATs really hot and went back to the Test Station the next day where it passed easily (CO = 0.02%). Before doing anything drastic, I suggest you give your car a good fast run on the motorway to clean out your 'clogged' CATs.
 

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Could the secondary air pump be the cause of the problem? If the CATs are cold and the air pump is blowing air into them, would this give the same symptoms as an air leak?


the car should be up to normal temp before a cat test is carried out & in this case the air pump should have switched off , best idea is a good thrash before the test .
 

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sound's like you've either got a leak in the exhaust or a lambda sensor playing up generally codes are stored when there is a failure it could that the lambda sensors are still working just not to there full potential.
in truth if the cats aren't rattling inside and there is no restriction to the back pressure then the cats are not blocked or broken up so i would never replace them
it is amazingly rare for a cat to loose its emission reducing properties without blocking or breaking up.
 

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Discussion Starter · #11 ·
It's a year since I posted the the original thread and the car has just gone through another MOT at 122k miles. Same scenario as last year - had to rev the engine to get the cats really hot for the CO figure to drop below the 0.20% limit (even though I had given it a run down the motorway). Lambda was spot on at 1.00. Engine is running fine - no knocking and not burning oil .
 
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