Audi S5 Timing Issue Causes Power Loss and High Fuel Use

Having dealt with a similar issue on my 2013 S4 last year, I can share my experience. I have moderate technical knowledge from maintaining my own vehicles. The symptoms you describe match exactly what I experienced, engine light, power loss and increased fuel consumption. The misfire pattern and timing issues between the crankshaft and cam sensor readings indicated a failing crank sensor in my case. I initially tried cleaning the sensor area, but this provided only temporary improvement. The workshop confirmed the crank sensor was defective and needed replacement. The total repair cost was 340 Euro, including parts and labor. The job took about 2 hours. The fix completely resolved the sluggish performance and engine light issues. Fuel consumption returned to normal and the engine ran smoothly again. Before giving more specific advice, could you share: Current mileage on your S5, Whether you notice the issues more during cold starts, If the engine light is steady or flashing, Any unusual sounds or vibrations This information would help determine if your case matches what I encountered with my S4.

Thanks for the detailed response. My mileage is currently at 108445 KM. I notice the issues are most severe during cold starts, and the engine light remains steady, no flashing. The engine synchronization problems seem worse in the morning. No unusual sounds, but there is a slight vibration when accelerating. Had my latest service about 3000 KM ago where they did a standard maintenance check, but these symptoms only started last week.

Thanks for the additional details. The symptoms on your S5 are nearly identical to what I experienced with my S4, especially the cold start behavior and steady engine light. The mileage is also in the same range where these issues typically emerge. The morning cold start problems and timing synchronization issues strongly suggest the crank sensor is degrading progressively, just like mine did. The fact that it started after your recent service is typical, these sensors often begin failing without warning, regardless of routine maintenance. In my case, the vibration during acceleration was also present, caused by the engine timing being slightly off due to incorrect signals from the failing crank sensor to the engine control unit. This affects the engine synchronization between the crankshaft and camshaft positions. Based on the timing chain being relatively new from your service history, I would focus on the crank sensor replacement first. The repair should resolve both the power loss and cold start issues. The fuel consumption increase you are experiencing is likely due to the engine compensating for incorrect timing signals. Given the matching symptoms and similar vehicle age, I strongly suspect you will need the same fix I had. The repair is straightforward and the improvement should be immediate once completed.

Really appreciate all the detailed input. You have described exactly what I am experiencing with my S5, particularly regarding the cold start behavior and timing synchronization problems. The reference value discrepancy between the crankshaft and camshaft positions seems to be the root cause, just as in your case. The fact that my timing chain was recently checked during service gives me confidence that focusing on the crank sensor is the right approach. From what you have shared, the 340 Euro repair cost seems reasonable for the work involved. I will schedule an appointment with my workshop and specifically mention the crank sensor symptoms and timing reference values you described. It is reassuring to know this is a relatively straightforward fix that should restore proper engine performance and fuel efficiency. Will update the forum once the repair is completed to confirm if this resolved my issues as well. Thanks again for sharing your experience, it has been extremely helpful in understanding what I am dealing with.