SQ5 Diesel Idle Stall: Common ICV Failure Fix Guide

Had the exact same issue with my 2012 Q5 3.0 TDI last winter. As someone who does basic maintenance but leaves complex issues to professionals, I recognized these symptoms immediately. The engine would constantly stall at idle, especially after cold starts. The engine idle was extremely rough and unpredictable. After the check engine light came on, I took it to my regular workshop. Turns out the air intake system was heavily contaminated, causing irregular engine stalling. The technician found significant carbon buildup affecting the proper air flow. They had to perform a thorough cleaning of the entire intake system and replace several components. The total repair cost was 425 Euro and took about 6 hours to complete. Since the fix, the car idle has been perfect, no more stalling engine issues. These problems are fairly common in direct injection engines with high mileage. To better assist with your situation, could you share: Current mileage on your SQ5, When did the stalling first start, Any other symptoms besides the engine stalling, What error codes are stored This would help determine if your issue is similar to what I experienced with my Q5.

Mileage is 177979 KM. Just had my last service done 2 months ago. The error codes from my throttle body diagnostic scan point to an idle air control issue. After reading your reply, I checked the intake and found significant dirt buildup around the throttle body area. The stalling started about 3 weeks ago, initially only when cold but now happens frequently at any engine temperature. Other symptoms include fluctuating idle speed and occasional rough starts. The engine seems to run fine once above idle speeds. The check engine light started flashing last week during a particularly bad stalling episode. Based on your experience, sounds like I might be dealing with the same carbon buildup issue affecting the engine idle. Will get it checked by a professional since the idle control problems seem to be getting worse.

Good to hear back from you and thanks for the detailed information. Your symptoms strongly align with my experience. Based on the mileage and symptoms you described, this definitely sounds like the same carbon buildup issue I faced with my Q5. The flashing check engine light during stalling episodes is particularly telling, this is exactly what happened with mine before I got it fixed. The IAC valve often gets blamed, but in our engines, carbon deposits in the intake system are usually the root cause of poor engine idle and stalling. When my car went in for repairs, they found that the carbon buildup was actually worse than initially suspected. The idle air control valve was barely functioning due to the contamination. After cleaning the intake system, they also recommended replacing the air valve assembly to prevent future engine stalling issues. Since your mileage is similar to what mine was when the problem occurred, and given that the issues started after your recent service, I would suggest getting it checked soon. The progressive nature of your stalling symptoms matches my experience exactly, it will likely continue getting worse. One tip from my experience: make sure they do a complete intake cleaning, not just the throttle body area. The total repair might cost a bit more than what I paid due to current parts prices, but its worth preventing potential long-term engine damage.

Thanks for the detailed response and thorough analysis. This is exactly the type of insight I was hoping to get. Your experience with the carbon buildup matches my symptoms perfectly. Will schedule an appointment for next week to get the intake system cleaned and checked. From what you described, a full cleaning of the air intake system makes more sense than just replacing the idle control valve, especially given how the engine stalling has gotten progressively worse. My mechanic quoted 550 Euro for a complete intake cleaning service including the throttle body area. While its more than what you paid, it seems reasonable given current prices and the scope of work needed to fix the engine idle issues. Really appreciate the advice about getting the entire system cleaned rather than just focusing on one component. Will definitely make sure they do a thorough job to prevent future stalling problems.