Startup problem during warm days.

[Merimel]

Hello,
I own AUDI A3 8P 1.4 TFSI (CAXC engine 125 hp, DSG), but actually VW use same engine and I saw really decent specialist here on forum so maybe you will be able to help me.

Since some time (actually since i bought the car) I'm facing little issue during the startup, but it only occur when specific condition are meet.
There is strange high rev idle, around 1100/min, with shaking a car and really awful sound. It last for about one minute, and then everything back to normal. (see the film below)

This happens only:

• the outside temperature is more than 15°C (trough the winter it start us like a charm - no problems)
  the car is parked for several hours

It very first turn on after car is parked. If i turn off the car and turn it on again during this first minutestart, problem is gone.


Except that the car runs perfectly, no issues. no power lost. But it's worrying me if it going to damage my engine.

I was to the dealer several times (first they didn't have a clue, checked everything, no fault found,...checked again..)

Spark plugs, oil and filters(all), water pump and timing chain(fully) was replaced during last year.

Millage is: 130 000 km /80 000 miles

" onclick="window.open(this.href);return false;

Any one is is this something i need to be worried about and what can be reason of this?
Thanks!

-Damian

[Cuprabob]

On modern petrol cars, under certain parameters, the Secondary Air Injection (SAI) system operates for a short period of time on start up in order to heat the catalytic convertor up more quickly. Normally this is done by injecting air into the exhaust however on some VAG engines they don't have a SAI pump but change the fueling to give the same outcome, which is to get the cat upto it's optimum temperature to reduce emissions.

I don't know that system your particular engine uses but from what you describe I would say it's normal operation and nothing to worry about.

If you want more information just Google "secondary Air Injection system"

[Merimel]

Hmm but should SAI rather start on every cold start, so also on cold days (winter) not only during warm days (summer)?

[Merimel]

Hi, i hope you won't mind if I bump topic with some more news.
I asked my mechanic if we can disable SAI temporarily and try to start engine..
So with disabled SAI there is no difference

Any one have more ideas what can be root cause for this?