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Turbo & Catalytic converter replacement


I bought a 2010 Audi Q5 from an Audi dealership 10 months ago. It had 86k miles on the clock at the time of purchase, now around 92k. Lost power over the weekend and there is a slight shaking coming from the engine whilst idling.

Audi informed me I need to replace the catalytic converter as well as the turbo in one go. Question I have is that I have driven only around 6000 miles in the last 10 months, mainly short distances in the city with two or three long distance trips.

If the CAT as well as the turbo failed shouldn’t that be something the dealer that sold me the car should have picked up on in terms of initial signs of wear and possible failure?? These things don’t just fail over night and I would assume there would be a build up to this major repair.

Thanks in advance.

Would anyone know what going to fail on a 6 year old vehicle 10 months later , the answer is No.
Also you should get a second opinion from an independent shop.


I assume the car was sold “as is” without any warranty. I don’t see how they dealer could have known that 6000 miles and 10 months ago. I also assume the car drove fine when you purchased it.


Sorry, but it’s unanimous… the car is now yours to repair. :persevere:
But whenever you get a diagnosis that portends a large repair bill, it’s always wise to get a second opinion.


I understand the points being raised here and I thank you for the replies. My question is still whether the car should have given any early warning signs that the turbo/cat was on its way out? And the car never brought up any warning lights on the dash to say the engine wasn’t functioning properly, not even when I took it in to Audi. The diagnostics computer plugged in and the car didn’t spit out one error message. Only after stripping the engine did they say I needed a new turbo and cat.

This is where I am struggling to make sense of everything.

The answer to ALL of your questions is no

Cars are smogged when a dealer sells a used car

In your case, it most likely only required a plug-in test

They check that the mil isn’t lit with the engine running, you have the required number of readiness monitors completed, no fault codes which command the mil to turn on

In my state, the catalytic converter readiness monitor MUST be complete. It’s probably the same in your state. So that alone means it was fine . . . as per the pcm . . . at the time of sale

Since there was no dyno test, there was no tailpipe readings. So there’s no record of just how clean or dirty the emissions were at the time of the sale. No reason, anyways

Unless I hear otherwise, I’ll assume your check engine light is now lit with the engine running, and you have a P0420 catalytic converter efficiency code.

Unless the turbocharger was noisey and/or the car was noticeably down on power at the time of the sale, the guys at the dealership have no way of predicting it will fail in several months

Same thing goes for the catalytic converter

None of us is there, so it’s going to be hard to remote diagnose a catalytic converter and turbocharger

As the others said, I’d seek out a second opinion, possibly from an independent shop which specializes in VW/Audi. Or maybe a shop which specializes in cars which have failed a smog test

I’d also wonder about carbon buildup in the intake tracts - have they checked for that? It’s a known problem area.

For both the cat and turbo to be bad, did the turbo lose its oil seal, contaminating the cat? How do they know the cat is bad?

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Meh, I guess that depends where the car is sold. Dealer cars sales in WA are exempt from emissions testing, no smog check required to license the car.

The answer doesn’t matter. It’s yours now. Sorry.
The answer, however, is not necessarily. Turbos can go at any time, and there’s no way to assess a cat’s condition before it fails.

Shaking while idling does not sound like a bad cat or turbo.
Sounds more to me like a failing ignition coil, combined with an asinine service writer trying to drain your wallet.
All other speculation is moot until you get a second opinion.

I can’t speak to what’s exactly wrong w/your car, but, yes, both the cat and turbo could fail 10 months after they were both working perfectly. And that wouldn’t be an overly unusual thing to happen.

The cat is sort of like a plumbing fixture in your house, which can work fine one day, and be plugged up the next. I’m sure you’ve had that experience. It’s true if you took that plumbing fixture apart (or the cat) and inspected it inside and out you’d notice some sediment building up which would eventually result in a clog. But absent doing that, no good way to tell.

If you suspected a cat problem on a used car you were thinking of buying, you could ask your own mechanic for what’s called a exhaust back pressure test, that would cost maybe $50, and if you were willing to pony up a couple hundred dollars more, a full-scale emissions test. But that wouldn’t necessarily show up a cat that would fail 10 months later, but at least you’d have a fighting chance. Here in Calif you need a current emissions test to sell a car, so here that – the emissions test part – would have already been done as the normal process of selling a used car.

The turbo, pretty much the same, concur w/the comments above. Those gadgets spin really, really fast, with large centrifugal forces involved. Even a tiny amount of imbalance can throw them quickly into death spiral. If the turbo was taken apart 10 months ago they’d likely find some imperfections. But nobody’s going to pay thousands of dollars to take it apart and inspect it w/no symptoms. The only practical way to rule out future turbo failure is to avoid car purchases w/turbos.

BTW: I wouldn’t recommend to have a dealer shop fix either of these problems on a 2010. Best to have that work done by a well recommended inde-shop who specializes in European cars.

I do not know about the cat, but I have seen many turbo"s fail buy shutting engine off without leaving the turbo spin down for a least 3 to 5 minuets. As @GeorgeSanJose said they spin very fast & stay spinning after shutdown ror a few minuets with no oil being pumped to the bearings.

Debris from a failed turbocharger can damage a catalytic converter, an experienced technician will check for damage before writing the estimate. Lack of experience results in accusations of dishonesty.

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Good point Nevada. In addition, oil being drawn into the induction system past bad seals in the turbo can result in contamination of the catalyst, killing the cat converter prematurely.

For the OP’s edification, a turbo has two sides; on driven by the exhaust system at a higher than ambient pressure, and the other pumping air into the induction system (the intake). The lateral wall pressure of the induction side will be lower than ambient pressure. There’s a bearing between the two sides lubricated by the engine oil. Seals prevent the oil from getting drawn into the engine. If the seals fail, the oil can get pushed by the exhaust side and pulled by the induction side and sucked into the engine. The residue from it burning can coat the catalyst in the converter and render it ineffective. The NOx needs to come in direct contact with the catalyst (platinum-palladium) for the cat converter to work.