When I start car when it is cold about 1/2 second after turning over I hear like a quick three stage rattle coming from engine compartment about 1/2-1 second long.The car revs fine is faster with strat intake I see no engine lights and idles smooth.Is this sound a plastic flapper in the stock intake system or do I have a potential valve problem.Being that there is no engine light a diagnostic test would not say anything is wrong so I guess I will just waite for it to go.Anybody have the possible answer.It does not have a mettalic sound more of a plastic sound.The rattle that is.When car is warm no sound at all.

 

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Thanks for reply, all other input or expieriences appreciated.

 

It could be the timing chain tensioner, power steering pump, or some other electo-mecanical control or device booting up. Goes away in a matter of seconds. Idiosycratic to this engine. I would not wory about it.

 

And logged many posts re: my saga with this phantom noise.

The first time I heard it I freaked. And it kept happening. But it was strange because it wasn't every time I started it. I took it in to the dealer twice to have it checked out. The first time, the car didn't do it for them. (Just my imagination...) The second time, they heard it but couldn't figure out what it was because it wasn't repeatable. But they checked everything out, tightened up any engine covers and said 'call us if it happens again.' My thinking at this point was, "why?" So, I got the car back. It did it a few more times. But I wasn't going to take it back. They were clueless.

Over time, the noise gradually subsided. I have 5000 miles now and I haven't heard it in probably a month or more. When I was posting about my problem, others on the forum wrote that they had the same noise when new but it went away. It appears mine has too. And so will yours.

What the problem is is open to debate. Chain tensioners? Very possibly. There was another theory floating, but I have it on my computer at home. Can't remember it now. But, all in all, the noise is, strangely enough, "normal." The word normal typically would carry the connotation that everyone with this car can expect this noise, but that's not the case. (In fact, you would think that there are little to no build variations from car to car given the "german engineering" and ultra tight build tolerances. But that's not the case, which is why some people have squeaks and rattles or engine/tranny problems and most don't.) In this case, "normal" means that 'some' S4s will have this noise and it is not an indication that there's something wrong with the car. Again, it will go away as your engine gets more broken in.

 

Took my car to the dealer today for it's 5K service. One of the items on my agenda was for them to check this "rattle" that happens at startup.
I have been told that what I am hearing is the timing chain tensioner, and that some S4's might experience more "rattle" than others, hence the reason why some do not hear it as much as some of us others do. Bottom line, it is "Normal" and there is really nothing to fix.
Like I said before, I have learnt to live with this "normal" rattle and consider it an idiosyncrasy of the car.
I have an A4 1.8T loaner right now (zzz..), which makes me appreciate more than ever the beast we all own here. I miss my rattle!

 

Have a cab with less than 1K miles. Only hear it on cold start, which is why I was concerned that dealer would not detect. Still assume it is normal, but some report they don't have...