Very rough idle RS5

[altobeast]

I have a 40k miles RS5 that I recently acquired, had inspected by 3rd party and got the green light mechanically. I have noticed that for the first 20-30 seconds on cold start, there is this harsh rattling noise as if something mechanical is rubbing or being shook around. Others have noticed this noise, but it goes quiet as a mouse after 30 seconds, into a pleasant and constant idle, no surging or pulsing or vibration. The start up is not accompanied by vibration, belt/chain noise, or anything like that.

Is this normal to have something like occuring? Would my Audi dealership be able to take a look and get this fixed or is it generally a problem that they'll say "happens" and charge me the diagnostic? I might try and run a Vagcom to see if any misfires are occuring, but have not yet.

Anybody else in the same boat?

[spa]

Sounds like a normal cold start.. ?

[2012s5cj]

Can you post a video or audio clip?

[altobeast]

I wasn't sure, I just recently got this vehicle and upgraded from a econobox, so this whole thing is new to me. It sounds rougher than I would like, but I have not had a reference to compare to.


I'll get a noise clip once it cools down from my commute in a few hours.

[2012s5cj]

I wonder if this is exhaust rattle if something is loose. Try revving it up in park and see what you hear. Drive with the windows down and listen carefully. Pop the hood, fire it up, and listen. Check for smells and leaks under the car. If everything checks out and you aren’t throwing codes, depending on how bad it sounds, I may not worry about it. Cars will have some rattle to them.

[altobeast]

I wonder if this is exhaust rattle if something is loose. Try revving it up in park and see what you hear. Drive with the windows down and listen carefully. Pop the hood, fire it up, and listen. Check for smells and leaks under the car. If everything checks out and you aren’t throwing codes, depending on how bad it sounds, I may not worry about it. Cars will have some rattle to them.

Thank you, I will do just that! No codes, may actually be exhaust rattle which is aggravated by the vibrations during a normal cold start. No leaks that I can see and I will smell today.

[2012s5cj]

No problem, man. Hold off going to the stealership until you try some of this stuff and save your $$$. The audio clip should be very telling.

[Delasangre4231]

I just got my first RS5 too and when I cold start mine it does kinda make a weird sound while it holds the RPM at 1500 or so for the first 30 seconds, to me it almost just seems like a miss-fire or like a little pop in the exhaust from the extra cold start fuel, I assume its normal as the car is amazingly smooth after the first 30 seconds.

[namvar]

mine's pretty smooth. At 40K it should still be under warranty.

[altobeast]

mine's pretty smooth. At 40K it should still be under warranty.

It's fairly smooth, just cold started again but didn't get a video :( . It is not under warranty due to time, but it seems more like fan and blower noise, I was in a garage before and it definitely amplified the noise. Some mechanical noise, but nothing super excessive, I believe it's a loose exhaust which is making some noise.

[Sazexa]

If it's idling rough at that mileage, and more so at start up, it could be an indicator of carbon build up.

[altobeast]

If it's idling rough at that mileage, and more so at start up, it could be an indicator of carbon build up.

Smooth as silk normally, just the first 30 seconds. How would I go about diagnosing that, I know that Audi has put up resistance on that problem.

[Ape Factory]

It's most likely just the cold start routine. Depending on what ECU firmware you're running, you'll get pops and crackles as it's dumping in fuel to heat the cats up quickly. The gas can ignite on the catalyst. The rattle could be a heat shield. But it definitely mean and grumbly on cold start and then should settle into a nice smooth idle.