A8 TFSI Idle Control Problems: Common Fix Found

I faced a very similar idle control issue with my A6 3.0 TFSI from 2011. As someone with some hands-on experience maintaining these engines, I can share what worked in my case. The symptoms were nearly identical, unstable idle, stalling engine when warm, and the engine running smoothly only at higher RPMs. Initially thought it was just the IAC valve, but the problem turned out to be more complex. Took it to a workshop where they diagnosed severe contamination in the intake system. The carbon buildup was affecting the proper air flow, causing the erratic idle behavior. The complete service included: Deep cleaning of the intake system, IAC valve inspection and cleaning, Air flow sensor check, Computer system reset Total cost was 425 Euro and it completely resolved the stalling engine issues. The idle control is now perfect, even after the engine warms up. Before suggesting specific fixes for your case, could you share: Current mileage on your A8? When was the last time you had the intake system cleaned? Are you noticing any other symptoms besides the rough idle? Have you scanned for specific error codes? This information would help determine if your issue is similar and whether the same solution might work.

Just had my last service at 102996 KM and the technician found the issue was mainly caused by carbon deposits in the throttle body. After a thorough cleaning of the IAC valve and throttle body, plus a new air filter, the idle speed returned to normal. The car runs smoothly now at all engine temperatures. If you need the exact error codes from my case let me know.

Thanks for the update on your A8, that matches my experience exactly. Had almost identical mileage when the same issue surfaced on my A6. It reinforces what I found during my repair, these 3.0 TFSI engines are quite sensitive to carbon buildup around the throttle body and air intake system. The stalling engine symptoms we both experienced are classic signs of restricted airflow. One thing I learned after my repair is that regular throttle body cleaning can prevent these issues from recurring. Since having mine serviced, I schedule a basic air intake cleaning every 30000km or so, much cheaper than waiting for the air valve system to get completely clogged up. Good to hear your car idle is back to normal. The combination of cleaning both the throttle body and IAC valve seems to be the winning solution for these engines rather than just replacing parts.

Thank you both for sharing your throttle body cleaning experiences! Its great to know I made the right call getting this fixed early. The idle speed has remained perfect for the last few weeks. The total repair bill including parts and labor was 395 Euro, which seems reasonable given the thorough cleaning work required. In case anyone else has a stalling engine issue with these 3.0 engines, the main error code I got was P0505 related to idle control. Will definitely follow the advice about regular air valve maintenance going forward. Planning to have the throttle body cleaned during each major service rather than waiting for problems to develop. Much better to prevent these issues than deal with an unstable engine idle later.