New Cat??

[Damo]

Had a fault code come up and the CEL light on.

It's P0420 - Cat conv. system, Bank 1 efficiency below threshold.

Garage says I need a new cat.

Currently running the A&M 3"DP with 100cel cat.
It's been on the car for just under 2 years but when the garage hitched up the emisssions gadget it was quite far above the maximum acceptable levels on a fast idel (idle was ok).

Is it fooked?
If I have to buy a replacement (BF for example) will the mapping need adjusting?

 

[acidstrato]

no mapping needed but as the cat is part of the dp u either need a whole new downpipe or get a replacement cat and have abit of cut an weld work done.

any symptoms? power wise?
tried clearing the fault to see if it returns?

 

[Damo]

Power-wise it seems fine. No other symptoms either. Seems to be running very well.

I've had the fault code cleared but I'm guessing it'll come back. I was watching the monitor on the emissions tester and it was well above what it should be.

 

[acidstrato]

its gonna be higher than what it should be though as you have a less restrictive cat..guess it depends if its out of the MOT pass range

 

[Damo]

It's miles out. I think the upper limit is .2 and mine was fluctuating between .3 and .65.

MOT isn't due for a while (and they may pass it anyway.......sshhhhh!).
Can't damage the engine in any way can I?

 

[acidstrato]

not that i can imagine, after all some people run decats

 

[Damo]

I'm going to wait and see if this fault code comes back up again.

Would changing the pre-cat lambda sensor have any effect on this (emissions)?
Previous searches suggest this may be at fault but I'm not sure if it's actually going to make any difference.

 

[Damo]

Had another fault code come up.

Maff signal too high (it's a new maf). Could this have any relation to the above?

 

[Craig!]

CAT threshold will be too low... your running a 100 Cell yet standard cars have around an 800 Cell so the engine picks up on this at times.

 

[ibizacupra]

Which aspect of emissions read high?
HC or CO or both

lambda control should control, and is part of the test, so if its holding lambda of 1 within their test spec, then lambda precat would seem ok, but post cat maybe not (or it is in fact confirming cat is catalysing well enough, as confirmed by MOT station sniffer)

Also, any leak in your exhaust system can affect the MOT tailpipe sniffer, even small one which can allow air to be sucked in.

 

[Damo]

Cheers for the advice all.

I'm going to go back to them and get them to check lambda values and also for small leaks in the exhaust. The cat isn't even 2 years old so I'll be gutted if it's buggered.
CEL light came back on again this morning which is probably the same fault code (that light is becoming a permanent feature on my dash).

 

[Damo]

Which aspect of emissions read high?
HC or CO or both

lambda control should control, and is part of the test, so if its holding lambda of 1 within their test spec, then lambda precat would seem ok, but post cat maybe not (or it is in fact confirming cat is catalysing well enough, as confirmed by MOT station sniffer)QUOTE]

Bill,

Just spoken with the garage.

My HC was fine.
O2 was fine.
Lambda was fine.
CO2 on idle was 0.10
CO2 on fast idle was 0.80.

Doesn't really mean much to me tbh. Any help on uderstanding what that means would be appreciated.