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Hi Guys,

A little help needed. Car failed on emissions so the garage changed only one of the cats out for a spare one that a previous customer had. Any way i checked the work once the car was home and noticed the cat was different to the original one that is still there. Then later that day the exhaust emission light came on and found out its a problem with an O2 sensor. Maybe the spare cat had a faulty sensor already installed. So i need a new sensor i believe but what about the cats being different to look at? Would this cause the light to come on the dash and would it effect the performance of the car?

Thanks

Gaz

Who did the work? Audi. How did they have a cat that fitted??

Could be the cat flows more or is different internally and throws up a code

Hi. No it was an car garage that does make up exhaust systems and had an old one sitting about that i is suppose to be good. That's what I was thinking. Car is still under warranty as I just bought the car so will be going back and demanding them to change it for the same one.

Is there just the one type of cat for the rs4.

yeah take it back to the garage,the main cats are 200 cell and rarely ail, id say it was a lambda giving a bad reading, the cat that has been fitted could be very poor quality (most aftermarket ones are) and will flow more gas throwing a code.

you need to see what the fault code is

Is it too simplistic to put the old cat back on and give it the old italian tune up? I went for a 30 minute burn before my last MoT to make sure that it was all hot and the emissions were well below limits; which is not to say that they would have been any different if I just rocked up cold, but it can't hurt.

I used to have an 8L S3 that once failed on emissions and the garage was all up for selling me new cats. Took the car out for some spirited driving, back in to test the next day and all good.

I had the same issue with the car failing on the MOT did the Italian Job ran it straight back to the MOT station and I passed.

Thanks for the advice. I think maybe putting the old cat back on and giving the car a good run would probably fix it. I just hope the haven't thrown the old cat out. Maybe just need the new 02 sensor. Thanks.