Car struggled on first start up.... but just once!

[PipRS6]

Hi all

Bit of an odd one.... a few days ago I started my car up and it was all over the place. I wasn't anywhere near the throttle but it was reving up to 2k and then dropping down to almost stalling. I gave it maybe 10 seconds to sort itself out but it didn't so I turned it off, started it again and it started up fine, and has done every time since. Any one have any suggestions?
The only thing I have done different recently is filled up with Tesco 99 because the Shell near me has closed for refurb. It is mapped on V Power so that's all I use normally. But I haven't driven it hard since that fill up so I can't believe that's the cause!
Any and all suggestions welcome!

[Ben_r1]

It can’t be the fuel otherwise it’d be persistent fault, from what I hear of late Tesco is better than vpower anyway...

I don’t know what could cause it specific to this vehicle but if I had to hazard a guess? Had a similar thing a few years back with a Clio 172, it turned out to be the idle control valve trying to recalibrate with every new start which led back to an intermittent TDC sensor fault.

Vag Com will be your best bet, scan and see what codes are there relating to potential idle issues.

[Shoppinit]

Mine very occasionally has a spaz where it’ll rev too high after starting. It’s done it twice or 3 times since I’ve had it. IIRC there was a fault code for comms between the ECU and TCU. No MIL since it didn’t reoccur. Next start was always fine.

I think that occasionally at startup the CAN bus trips over itself.

Having said that, I only ever had fast idle when this happened not hunting so your cause may be something completely different.

See if there are any fault codes.

No separate idle regulator on the RS6. The ECU does it all.

[PipRS6]

No fault codes other than the SAI one which is always there.... I wouldn't say it was hunting as such, it was revving high and then spluttered and dropped down and nearly died and then straight back up high again. Did that twice but otherwise it was just high.....

I will keep an eye on it and see if it happens again. But otherwise I won't worry!

[Banana man]

How long was it before it was started previously? My s4 had been laid up for a fair while and coughed and spluttered until it bled of air and the injectors cleared themselves, fine afterwards.

[PipRS6]

How long was it before it was started previously? My s4 had been laid up for a fair while and coughed and spluttered until it bled of air and the injectors cleared themselves, fine afterwards.

Parked up the evening before and this was first start the next day. Its my daily so gets driven plenty.