S8 Timing Sensors Causing Power Loss and Poor Performance

Had a very similar issue with an S6 from around the same period. With some experience working on these engines, I can share what worked in my case. The symptoms match exactly what I experienced, engine light, power issues, and the ECU showing timing reference problems. Initially thought it was the timing chain, which had me worried about repair costs. But the actual culprit turned out to be a faulty crank sensor causing engine synchronization issues. The workshop diagnosed it using proper diagnostic equipment and found the crankshaft position sensor was sending incorrect signals, leading to timing mismatches and occasional misfires. They replaced the sensor and reprogrammed the ECU to properly recognize the new component. Total cost was 340 Euro including parts and labor. Before suggesting this might be your exact issue, could you share: Engine type and year of manufacture, Any unusual sounds, especially during cold starts, Whether the check engine light is constant or intermittent, If you have access to specific error codes This would help determine if your case matches what I experienced or if you might be dealing with a different timing-related problem.

After 49217 KM, I am experiencing the exact same symptoms, engine light with power loss and timing reference issues. Recently had my service done but the problem persists. My crankshaft to cam sensor readings are also showing incorrect reference values. What caught my attention in your fix was the sensor replacement being sufficient, as opposed to major timing chain work. That could save significant repair costs. Was the engine running rough before the sensor replacement? In my case, there is a slight vibration at idle which makes me wonder if I am dealing with a misfire caused by the same sensor issue.

Glad to follow up on this. Yes, my engine had similar vibration issues at idle before the fix, and it definitely sounds like what you are experiencing. The misfire was directly related to the faulty crankshaft position sensor throwing off the timing signals. The slight vibration you mention is a telltale sign, in my case, it was most noticeable when the engine was cold and would somewhat smooth out after warming up. The timing chain itself was intact, but the incorrect signals from the bad sensor were causing the ECU to adjust timing incorrectly, leading to those misfires. What convinced my mechanic to start with the sensor replacement was that the timing chain showed no physical wear during inspection. The misfire pattern was also consistent with sensor-related timing issues rather than mechanical timing chain problems. After the crankshaft sensor replacement, both the vibration and power issues disappeared completely. The repair has held up perfectly for the past 60000km with no recurring issues. The cam sensor readings returned to normal ranges and fuel consumption improved back to standard levels. If your symptoms match this closely, I would recommend having the crankshaft position sensor checked before considering more extensive timing chain work. The diagnostic process is straightforward and could save you from unnecessary repairs.

Thanks for sharing those details about your fix. The idle vibration I am experiencing matches your description perfectly, more noticeable when cold and slightly improving after warm-up. Your feedback gives me hope this might be resolved with a sensor replacement rather than major timing chain work. I have scheduled an appointment with my mechanic to specifically check the crankshaft position sensor. The fact that your repair has lasted 60000km without issues is particularly reassuring. The misfire symptoms and timing reference values being off align exactly with what you experienced. Will have them focus on the sensor diagnosis first, as starting with the less expensive repair option makes sense, especially since the timing chain shows no obvious signs of wear. Really hoping this resolves both the engine light and the power loss issues like it did in your case. Thanks for the detailed insight about the repair. Will update once I have more information about what they find with the sensor readings.