It's a bit of an essay but worth the read for anyone who might be able to help:
Our car's just failed it's MOT on emissions (independant Council MOT test centre), for the second time in a row! Following last years failure, the CAT and Lambda sensor were changed (I think the Lambda was OK, but garage insisted it was faulty!). The rear box was replaced just before the MOT in 2009, and then following the MOT test, the CAT and Lambda were replaced.
The car then scraped through the emissions. Here's my question:
Additional info: I took the car to an independant Pug and Citroen specialist to have the head gasket replaced soon after the 2009 MOT pass and they spotted exhaust paste up stream from the CAT, which is a "no no :nono: " and told me to take it back and get it cleaned off. The other garage did so reluctantly.
I'm taking the car back to the garage that fitted the sensor and CAT and ask them to check the emissions and more importantly get the CAT replaced FOC (under warranty) if it is, as I suspect, a dud aftermarket CAT that's not up to the job. However, does anyone know of what else might cause the emissions to fail other than the CAT?
Thanks in advance of any help/advice you could give me ASAP.
That's a marginal fail on the CO2, looks like more an efficiency/adjustment issue that something broken. The lambda test average is within spec so I can't see it obviously being cat related. I'd slap in a quadruple dose of Forte fuel system, injector cleaner, and get the engine seriously hot (as in a 20 minute motorway thrash flat out in 3rd seriously hot) and that might well do it.
Failing that, new plugs and air filter may help. Cleaning and adjusting the TB may also be required. I can't see that being anything more serious.
That's the problem with the Carncil MOT places - they do exactly the same test, to the same standard as any other reputable MOT station (if they're passing or faiing cars beyond a few percent of the national average, they send the spanish inquisition round to check), yet aren't best placed to advise on what the cause of a minor failure might be.
I stomach the cost and get mine done at the Pug dealers for several reasons - they are familiar with the model so are aware of any MOT exemptions or bulletins relating to the vehicle (such as the allowable 3mm play in 407 swivel hubs, which would fail at any other test place), they are best placed to advise if a car should fail, and it's simply more likely to pass and less likely to be failed for something spurious simply because a tester knows what-should-be-what on a pug. Never had one fail yet.
The Forte Injector cleaner sounds pretty good from what I've read, only problem is that my wife just filled the tank up the day before the MOT! I'd drain 3/4 of the tank but I don't know how to get the fule out, without it getting messy (any ideas?). I could drie the car around but at £1.10+ a litre, I'd rust the car from my tears!
Also, you mention adjusting the TB, I've got no idea what that this (Timing Belt?).
I'll check the plugs and filter, but they looked OK to y untrained eye when I last checked them.
I know what you mean about, "MOT only" stations, but the perception of them not being in it for anything other than to ensure car fit for the road is what appeals, having had some bad experience of garages in the past "creating" work that didn't need doing. Now my cynicism is biting me in the "big end". You feel like you can't win.
Sorry, TB = throttle body. You can buy foaming cleaners that you spray into the inlet tract, but I'd be inclined to remove it, strip it properly, clean it, and reassemble it and have it properly set up an a gas analyser.
I don't know how the idle air control valve affects emissions, the oft misnamed 'stepper motor', on these, (I think it leans it down at low revs to help the engine idle properly and not bog down when feeding in the gas like the Vauxhall system did on the SE series motor) but it's but the work of a moment to remove and check/clean that as well.
One can never be sure without the car in front of you, but my gut feeling is that it's nothing too fundamental.