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172Cup Emissions Light

  RS Clio Cup172
Hi everyone, I have been searching and checking symptons but nothing quite matches so far.

My 172 cup has been mine its whole life and is now on 93,000 miles.

Its only mod is a ktec silenced exhaust system from the cat back fitted 4/5 years ago.

Yesterday as I was going 50mph on motorway the emissions light flashed on, then cleared, this happened every 3 miles. I noticed the car also especially in second gear was no longer smooth but 3rd 4th and 5th gears ok. Anything above 25mph really.

Their is a distinct new smell as well - metallic. My grandads honda civic had similar symptoms and it turned out it was the catalytic converter.

It is booked into the garage on Friday but if I can get any more ideas that would be great. If it is a cat, who is the best aftermarket?

It starts first time and idles smooth and as usual.
The plugs, oil were done early autumn.

I cannot smell any fuel leaking at all.

Many thanks.


ClioSport Club Member
First, do not give up your OE cat (they’re worth £500-£600 scrap)

Secondly it’s unlikely just to be a dead cat it’s more likely you have an injector issue (very common on these) and will be dumping too much fuel in.


ClioSport Club Member
  FF Jeden Osiem Dwa
Have you had a code reader on it? I've had my engine light flashing like Blackpool illuminations for the last 2 weeks and code P0300 random misfire. But I was getting a distinct smell of fumes and unburnt fuel inside the car.
It struggled through the emissions test back in September.
I changed the front lambda sensor and injectors yesterday and it's spot on now. Feels alot smoother and like there's a bit more power.
Mines on 97k miles. I think Bosch recommend changing the lambda sensors every 90k miles.