had my alternator changed & since I had it back, the car takes a few seconds longer to return to idle speed. When driving it seems as the engine is running a little faster than it should. I've even had the revs raise a little without me touching the accelerator...

4 hours ago, car134 said:

had my alternator changed & since I had it back, the car takes a few seconds longer to return to idle speed. When driving it seems as the engine is running a little faster than it should. I've even had the revs raise a little without me touching the accelerator...

Sounds like the battery management system thinks the battery is in a poor state of charge?

Why was the alternator replaced?

AA said battery wasn't getting any charge, had a red warning light telling me battery wasn't getting any charge. 

Was it replaced under warranty? Does your start/stop system work correctly?

no, not done under warranty. Don't use the start/stop tbh 

The start stop display can be a great indicator of unusual behaviour. It might be worth having a look at it the next time you're out and about.

ok ty, will do !

When you say don't use start stop do you mean you turn it off with the button in the console? 

 

Are you aware that raised idle could be due to having heavy battery demands. Like having ac on heated mirrors and lights. And if tdi engine DPF regeneration. 

I've owned the car for 4 years & never had this problem, I've done 120,000 miles. If it was in re gen mode you can smell it when it's regenerating. The start stop is turned off via button