CAT failing

[SteG]

How long do we expect a catalytic converter to last?

Just had mine in for MOT and the tester informs me that it will not pass next years MOT as it is on the limits now (2% ). Can we adjust mixture settings on the standard set up?

Car is an August 2013 1.6 sigma with 4.5K on it. Lack of use could be one reason but it does get used (very hot) when I'm out.

Would have expected it to last a bit longer than this. CC replacement nearly £600

[Jonathan Kay]

That sounds far too early.

Have you got all the exhaust concentrations from the previous tests?

Jonathan

[SteG]

Jonathan,

I will have them in the archives somewhere but I seem to remember it was 1.7% 12 months ago but will need checking when I'm at home. Was thinking of sounding CC out to hear their views.

[JNC]

Look for a seven friendly MOT station who knows what they are doing 

[The_ASH]

I’d check the lambda sensor first as this can cause higher emissions, Seven catalysts do eventually fail like any car but not usually at the age/miles you list and as JNC suggests find a local Seven friendly garage as it sounds in this case that the MOT tester might be faulty rather than the CAT?

Useful info by Hella here

[ChrisC]

Was the cat hot at the MOT station? 

Lambda sensor is a good shout, know to fail on Sigma cars (for some reason) all be it still very early.   Do you know someone at your local meet with the MBE lead and how to diagnose your current sensor?

Also was it running long enough before reading was taken.  The ECU won't use the lambda reading to adjust the mixture until the 30 seconds after the engine has started (lambda sensor warmup time) and the coolant is over 67C.   That 30 seconds is regardless how warm the engine is, and how long the engine was stopped for, you can normally hear the end of the 30 seconds if the engine is warn, when it comes off map only and onto map and lambda feedback.   My 2011 Sigma was very rich during that 30 seconds, then spot one. 

Plan B - By pass pipe and swap in the cat for MOT.  It's cheaper than a cat, and might give you a few more years before needing a replacement. 

[The_ASH]

I’d work out whether the sensor is faulty and go with Plan B myself. Rectifying a faulty Lambda could actually pay for itself over time if the ecu is over fuelling.

[Nick Bassett]

Personally, I would try and find a 'Caterham friendly' MoT station... they are out there.

[ChrisC]

Get someone in the know at your local meet to plug the lead into your car.   If all is good will only take a few seconds.  The lambda sensor from bosch is over £80 and more for the ford part.   I know there are cheaper alternatives but I feel with this sort of thing its a case of buy right buy once, and also, know whats needed before you buy.     There are other sensors that could also play up, for example the MAP sensor.  On a 150 this was left open to the air and easy to get killed with water ingress.   Dependent on your sigmas spec the air tube to that MAP sensor could have become damaged, that would also explain the problem. 

A local club member had spend a fair few hundred quid on sensors for his duratec trying to find a intermittent running problem.   The lead found the problem (with a bit of diagnosis), end result the inertia switch was intermittent, how many engine sensors would have been replaced before he got to that if he was just using guess work.

  

[Jonathan Kay]

I would try and find a 'Caterham friendly' MoT station... they are out there.

I suggested that we share experiences on this... with a map, but was laughed out of court. And yet we're openly discussing elsewhere how to make a car illegal on public roads...

Jonathan

[ChrisC]

Yep my 5 min task to swap the cat back onto the car for MOT has now turned into "take the cat in a plastic bag along to the MOT"

[SteG]

Many thanks guys. Food for thought. I'll check out the LAMBDA first and find a 7 friendly test station. Interestingly it was tested by a certain Caterham dealer in Mid Cheshire.