A4 EGR Problems: Rough Idle and Power Loss Alert

I had nearly identical symptoms with my 2015 A5 a few months back. As someone with some experience working on performance vehicles, I initially thought I was dealing with a vacuum leak given the hissing sound. The check engine light and rough idle prompted me to take it to a workshop. Their diagnostic revealed a jammed EGR valve, which was preventing proper exhaust gas recirculation. The valve was stuck partially open, causing irregular engine performance and those classic EGR-related symptoms you described. The repair involved replacing the complete EGR valve assembly. Total cost was 355 Euro, including parts and labor. Since the replacement, the engine runs smoothly again with no power loss or smoke issues. To help provide more specific advice for your situation: What mileage is on your A4? Have you scanned for error codes? When did these symptoms first appear, gradually or suddenly? Are you noticing any specific driving conditions when symptoms worsen? While our cases sound similar, having this information would help confirm if you are dealing with the same EGR valve failure. In diesel engines these issues are more common, but they do occur in gasoline engines as well. Consider getting the codes read before visiting a workshop, this can help verify if the EGR system is indeed the culprit. Some auto parts stores offer free diagnostic scanning.

I have the same mileage issue at 190010 KM with identical symptoms. Got codes read last week which confirmed the exhaust gas recirculation malfunction. The rough idle is especially noticeable during cold starts. My mechanic suggested a complete valve cleaning first before replacement to potentially save on repair costs. If the cleaning does not resolve the check engine light and performance issues, a new EGR valve would be the next step. The emissions test also failed due to these issues, so addressing this has become urgent. The catalytic converter readings are normal though, which helps narrow down the problem to just the EGR system. Since my last service was only 2 months ago, this issue developed quite suddenly. Worth checking if your warranty might still cover this type of repair.

Thanks for the update on your A4 situation. The symptoms match exactly what I experienced with my A5 EGR valve failure. I would actually advise against just cleaning the valve in this case. From my repair experience, when these performance issues appear this suddenly and the codes specifically point to EGR malfunction, cleaning rarely provides a long-term fix for these automotive repair needs. In my case, the cleaning attempt only gave about 2 weeks of improved operation before the rough idle and vehicle emissions problems returned. The complete EGR valve replacement ended up being necessary anyway, so I essentially paid twice. The fact that your catalytic converter readings are good actually matches my experience. The EGR system operates independently, and when it fails, it causes those specific symptoms, especially that characteristic hissing and jerking during acceleration, without necessarily affecting other exhaust components. Since your mileage is similar to what mine was when the issue occurred, consider skipping the cleaning step and going straight for the replacement. It might seem more expensive initially, but could save money in the long run by avoiding temporary solutions. Keep in mind that continuing to drive with a malfunctioning EGR can potentially cause additional engine damage due to improper exhaust gas recirculation. Getting it fixed properly the first time is worth the investment.

Thanks for the detailed input. After considering your experience, I agree that going straight for the EGR valve replacement makes more sense than attempting cleaning first. The symptoms are too similar to ignore, especially the rough idle and emissions issues. I called the workshop and scheduled the replacement for next week. The quoted price is 380 Euro, which seems reasonable based on your repair costs. The failed emissions test really leaves no room for temporary fixes anyway. What convinced me most was your point about the cleaning only lasting 2 weeks before problems returned. No point wasting money on half measures when the valve clearly needs replacement, particularly with such clear diagnostic codes pointing to EGR failure. One question on the repair process though, did you notice immediate improvement after the replacement, or did it take some time for the engine management system to adapt? The vacuum leak like symptoms and rough engine performance are getting worse, so hoping for quick resolution once the new valve is installed. Will update on the repair outcome. Really appreciate the detailed insights that helped avoid the cleaning attempt detour.