wconstan

I have a 2008 RS4 convertible with 134,000 miles on it. It has developed a rattle on cold start that continues until the car is warm. The rattle is not dependent with RPM. None of the codes seem to indicate anything useful. I have attached a video. Do we think this is the dreaded timing chain? Something else? Given that it doesn’t change with RPM I would think it’s not driveline related, but I also don’t know much about timing chain issues. The car sits for long periods of time in a barn, we are afraid to drive it because of this issue and the shop is quite far away and would require a transporter because the car also has a warped disc so we don’t want to drive it on the highway. We’ve had it since new and it’s very special to us, but we are not sure how much more money we want to dump into it.

JohnnyJ

You mean that the rattle doesn't change frequency when you increase the rpm?

wconstan

Correct! I should have been more clear about that. The rattle does not change frequency or go away with RPM. It seems to go away once I actually drive the car, so not sure if it’s a warming up issue or a car movement issue. It does actually go away before the car is fully warmed up.

JohnnyJ

If it stays the same frequency while increasing the rpm, it cannot be the timing chain, it has to be a fan with leaves or other garbage hitting the blades.
What happens if you change the rpm of the cabin fan when the sound is occurring?
Also check the motor cooling fans for obstacles to the blades. NOTE: Disconnect the battery before touching those blades. The fan/fans can start even when the motor is stopped.

wconstan

Oh interesting! It makes sense to me that it isn’t timing chain if it doesn’t change with RPM. But I’m still confused by how abruptly the noise goes away, it goes from that noise in the video to silent almost instantaneously after time has passed, sometimes it seems to go away quicker if I start driving, other times it goes away when idling.

I have not played with the fans, cabin or otherwise, but I certainly will the next time I am near the car. It’s kept in a barn a family member owns 100 miles outside of NYC (where I live).

Do you think the potential fan issues would explain how abruptly the noise goes away?

JohnnyJ

Without guessing further, I'm awaiting the result of your investigation ... Just be careful with the cooling fans at the front.

MarkDoronin

I find your case interesting. What's your conclusion?

JohnnyJ

When people are asking questions and get a solution to their problem, they almost never get back and say "thanks" or the corresponding action in the thread. Sad!

wconstan

Hi All! Sorry for the delayed response.

I don't have a conclusion because I went to start the car and the noise just....wasn't there anymore?

It was a cold start, and the car had not been driven in a month. The same circumstances that have caused the noise for the last 2 years. I played with the heating and air conditioning and the noise did not come back. I took it for a 30 minute drive and the car came to temp as normal drove well (though I did discover my DRC is leaking badly so that's another thing to deal with).

The check engine light has been a problem for 30,000 miles and multiple shops (including two Audi dealers) have never been able to get it to go away reliably. I did plug in my code reader when it was at idle and got the two attached reports. I am new to using code readers so not sure how to interpret. The misfires certainly could be timing chain related, but I also think it's been at least 15,000 miles, though possibly much more, since the spark plugs were last replaced. I ran these two reports back to back. I did think it was odd that there was so much variation in the timing advance. Do those numbers look in spec? They looked odd to me but I haven't been able to find info online about what they should be.

Appreciate everyone's help as always! This car has had a lot of work done to it but was owned by a family member, who is not good at maintaining things and keeping up with oil changes, since new so I am a little worried about the long term future for the car. Just trying to wrap my head around how much this car may actually need.

RAudi Driver

That sound sounded like a struggling injector to me but what do I know. Since it's gone, it's a moot point.