Hiss on cold start up??

**walla** · 29th January 2012

Hi guys, i've got a a3 quattro and ive noticed something strange with my car. When starting up the car cold it'l rev at 1,200 rpm for a few minutes and then settle slowly down to about 800rpm. Now not sure if this is normal but it's always been like that.

However now ive noticed that just before it starts to drop there a very distinctive hiss. Is this normal??

**Westy** · 29th January 2012

Revs will always be higher on cold start and they will drop as the engine warms but yours might be a bit high.

If I was you I'd stick your head under the bonnet and see if you can pin point the hiss as it sounds like you might have a split hose somewhere.

**<tuffty/>** · 29th January 2012

Its most likely the SAI... if its hissing then it could be that the vacuum pipe has been disconected... yours had an N249 bypass or something?

<tuffty/>

**Dani_B19** · 29th January 2012

Do you have the aircon on when starting up? If my air cons on when i first start the car, you get a whining/hissing noise.

**walla** · 29th January 2012

Just stuck my head under the bonnet (luckily its cold outside so it didnt take long for the engine to get cold)

Theres definitely a small click before the hiss, almost like a switch clicking by the battery. The hiss it self is coming from the front of the car below the throttle body. Not sure if it makes a difference but i have the Electronic throttle on mine.

**MrCSW** · 29th January 2012

Sound like the a/c fan.. see if it does it with the climate set to Econ.

**walla** · 29th January 2012

The air conditioning/heater was off at the time.

**<tuffty/>** · 29th January 2012

SAI....

<tuffty/>

**<tuffty/>** · 29th January 2012

...or a vacuum leak from the PCV...

<tuffty/>

**walla** · 29th January 2012

any ideas on repairs costs etc.

and how it would affect my cars performance

**QuattroRich** · 31st January 2012

Originally Posted by walla

However now ive noticed that just before it starts to drop there a very distinctive hiss. Is this normal??

I have an A3 quattro and have this hissing sound coming from the same place. Only seems to have come about now the cold weather has set in and disappears once the engine has warmed up after a couple of minutes.

Can this problem be solved easily?

Thanks

**Reesy** · 31st January 2012

It's the SAI as tuffty said. My 2 tqs' have both done/do this...

**QuattroRich** · 31st January 2012

Cheers Reesy, will look into it

**Reesy** · 31st January 2012

Originally Posted by QuattroRich

Cheers Reesy, will look into it

Shouldn't need to mate, if it makes a noise and then cuts off as the revs drop, its more then likely working fine. Mainly happens when car and ambient temp are cold.