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D2 - Fuel and Exhausts Everything to do with getting fuel into the engine, and fumes back out again

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Old 6th October 2021, 12:40 PM
Simon Wallwork Simon Wallwork is offline
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Default Cat rattle.

I hit a pothole yesterday and there was a rattle afterwards, which persists.
Pretty sure it's from one of the cats.
I changed one on this car before, and the mechanic silenced the rattle with a hammer, but I still ended up fitting the oem cat.

Now, I'm in Bulgaria- and emissions don't matter here. The car is running well and I'll certainly give the thing a whack and see if it helps.

If I were to remove the cat, and poke out all the enviro-gubbins contained within, will it cause the car any problem?

Car is a 2000 model FL S8 btw.
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Old 6th October 2021, 06:50 PM
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Adrian E Adrian E is online now
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If completely removed you’re likely to get EML on as the post cat lambda probes will be seeing a rich mixture. That’s an MOT fail these days, although suspect plenty of dodgy testers remain that will emissions test another vehicle to get around it (god knows why as they’re putting their licence at risk)
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Old 8th October 2021, 09:53 AM
Simon Wallwork Simon Wallwork is offline
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Hi Adrian.
I'm looking for a cheap fix here.
We are in Bulgaria, having an EML on is no problem, except to me. You know what we are like!
So, I just need it to run, which it does, and function normally- no lights.

Two possible things I came up with.

1. Remove cat, give it a shake and loose bits might fall out- thus stopping the rattle?
2. I saw a youtube where a guy located the bad bit by listening very closely, then driving a self tapper in to hold it.

Or I could just keep the radio on....
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Old 8th October 2021, 10:56 AM
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Yeah, I understand was thinking about the scenario when you bring it back to the UK. With the EML light on, usual practice is for the ECU to default to a 'safe' map. It shouldn't cause you any problems as it won't go so lean due to what the lambda sensors are showing post-cats as to cause any damage - it will have been programmed to recognise the most likely scenario where pre-cat lambdas look fine and post-cat are way off to recognise the cat is the cause.

To stop EML without cats involves flashing the ECU to remove the post cat lambdas
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Old 9th October 2021, 01:42 PM
Simon Wallwork Simon Wallwork is offline
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Well, it's stopped.

I'm not getting too excited about this, but it would be good to know what others have done about this, apart from change the Cat.

I may as well post my own previous on this.
I came out one morning years ago, started the car and got this death rattle, which seemed associated with rpm.
I had to go to work, so after checking the oil, I drove very gently- thinking, 'Me car is fooked!'.
After work I took it to 'A for Audi' in Clydebank, fearing the worst.
Andy put it up on the ramp, engine rattling like a *******.
He smacked the cat with a mashie, and the noise stopped dead.

I've rarely been more impressed, in a garage.
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Old 9th October 2021, 01:52 PM
HPsauce HPsauce is offline
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Quote:
Originally Posted by Simon Wallwork View Post
I'm not getting too excited about this, but it would be good to know what others have done about this, apart from change the Cat.
I changed my cat (just one side needed doing) eventually, though by the time I got round to it the rattling had almost gone.

Turns out that the matrix inside had pretty much disintegrated and had almost entirely been blown out! So the exchange return didn't net them much in the way of rare elements.

Despite one side of the engine missing the cat I didn't get any warning light and it sailed through the MOT emissions just fine. 2002 build FL S8.
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Old 10th October 2021, 11:49 AM
Simon Wallwork Simon Wallwork is offline
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Thanks HP.
Good to know!

I shall follow your advice for the time being.
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