Hello, I'm new to the forum and would appreciate some help. U have an 03 A4 18t with idle problems. When the engine reaches running temp, the rpm gradually increase to between 1800-2000 rpm. I have to blip the throttle, and after a few seconds, the revs will drop to around 900rpm, but soon after, the revs will start to build up again. This process will continue to repeat itself. The engine has been fitted with a new throttle body but no change to it's characteristics. I am also getting vacuum when I open the oil filler cap. Thinking this a breather problem, I changed the pcv valve. The engine is also pinking under acceleration.  Before I commit to spending more money, does any one recognise any of these symptoms.  Any help would be greatly appreciated. 

Thanks in advance.

Welcome to the forum Neil, just out of curiosity have you had a diagnostic check carried out? And if so what fault codes flagged up? 

I'm wondering if it could be the airflow sensor. 

Cheers

Steve

Getting a diagnostic on wed, will let you know what the codes are. 

Thanks Steve