[Clarke2744]

Sadly my cat seems to have died on my 2015 PFL 8V - Not wanting to fork out the ~£2k for a new one and having been quoted ~£500 to have the EML coded out, I thought I’d keep an eye out for second hand stock primary Cat/downpipe. So if anyone has a working stock cat lying about they’d be happy to sell to me please let me know! Ideally southwest/Wiltshire/Surrey location.


Additionally if anyone has experience this problem before on a completely stock car - do let me know what your solution has been! It still passes MOT emissions fine, with the light ‘turned out’.

Thanks 👍🏻

Edited by Clarke2744, 21 March 2022 - 03:44 PM.

[0120raptor]

Personally I`d leave as is. £500 to code out seems expensive.

[RS777]

Personally I`d leave as is. £500 to code out seems expensive.

Surely someone knows a coder who can do it cheaper than that?

[Clarke2744]

Personally I`d leave as is. £500 to code out seems expensive.

My thoughts exactly - It passes emissions and I’ve been assured it won’t cause any damage to the car driving it with a knackered Cat, it’s merely the annoyance of clearing the code every fortnight. However I’m sure a working cat would be preferable for a buyer if/when I come to sell the car.

[RS3Dell]

My thoughts exactly - It passes emissions and I’ve been assured it won’t cause any damage to the car driving it with a knackered Cat, it’s merely the annoyance of clearing the code every fortnight. However I’m sure a working cat would be preferable for a buyer if/when I come to sell the car.

Just a thought if your RS passed the emissions are you sure it's the cat & not the O2 sensor as there's 2 fitted,one before the cat & one after,if either are faulty it will bring up a EML.

At a guess the 2nd one after the cat which it monitors is playing about.

Dell.

[Clarke2744]

I’ve replaced both pre and post cat sensors, with Bosch part numbers (the same as the OEM ones, just without the Audi number stamped on them). Sadly made no difference, other than the CEL coming on perhaps even sooner than 2 weekly.

[RS3Dell]

I’ve replaced both pre and post cat sensors, with Bosch part numbers (the same as the OEM ones, just without the Audi number stamped on them). Sadly made no difference, other than the CEL coming on perhaps even sooner than 2 weekly.

You've covered all bases there then,do you know what comes up if you scan it when the EML is up ?

Dell.

[Clarke2744]

Comes up with a P0420, cat efficiency below threshold.

[RS3Dell]

Comes up with a P0420, cat efficiency below threshold.

Ok have you check the emissions value at the last mot to previous ones & is there a big discrepancy ?

Dell.

[Clarke2744]

Values seem very similar.

Fast idle results compare as follows;
CO 0 last year, 0.02 this year
HC 4 last year, 3 this year
Lambda 1.020 last year, 1.005 this year

I’m no expert on emissions, but those seem very similar results.

[Clarke2744]

Had a look over the cat with an endoscope…. Im no Cat expect, but seems to have revealed what looks like a pretty big split along one side - see pic.
Fortunately I’ve got old of a second hand cat - so confirms it’s definitely the cat and not a sensor issue!

The rest of the cat looks in pretty good condition, no melting etc - any idea what could cause this split to occur? - I’ve always been pretty skeptical about the effect of the ‘bangs’ that the car makes in dynamic mode on exhaust components, but would have expected the cat and exhaust be designed to handle that?!

Attached Images

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Edited by Clarke2744, 26 March 2022 - 12:29 PM.

[RS3Dell]

Values seem very similar.

Fast idle results compare as follows;
CO 0 last year, 0.02 this year
HC 4 last year, 3 this year
Lambda 1.020 last year, 1.005 this year

I’m no expert on emissions, but those seem very similar results.

They do look good on idle not to bring up the EML but once your using power it may then see an issue.

Dell.