Audi A4 Timing Issues Causing Multiple Engine Problems

I had a very similar issue with my 2005 A6 last year. Having moderate experience with engine diagnostics, the symptoms you describe match what I encountered, engine light, poor performance, and timing-related fault codes. The crankshaft sensor was indeed the culprit in my case. The faulty sensor was causing engine synchronization problems, leading to those misfires and performance issues you mentioned. After diagnosis, replacing the sensor cost 340 Euro including labor. The good news is that while the symptoms can seem severe, the fix is relatively straightforward once properly diagnosed. The timing belt itself wasnt the problem, but the engine control unit wasnt getting accurate crankshaft position data, which affects timing and fuel delivery. Before jumping to conclusions though, could you share: Current mileage, When was the last timing belt service, Any specific fault codes from the diagnostic scan, Does the engine light stay on constantly or flicker This information would help confirm if your issue matches what I experienced with the cam sensor system. Also worth noting that a proper diagnosis is crucial, while sensor replacement is common, similar symptoms can sometimes indicate other timing-related issues that need attention.

Thanks for the information about the sensor issue. My A4 has 135088 KM on the clock, and the timing chain was last serviced during the most recent maintenance about 6 months ago. After running another diagnostic, I got the P0016 code which confirms the crankshaft-camshaft position correlation issue. The engine light stays on constantly now, unlike before when it was intermittent. The misfire seems most noticeable during cold starts and when accelerating. Based on your experience, it sounds like I should focus on the sensor rather than worrying about the timing components. Would you recommend checking both camshaft and crankshaft sensors, or just start with one?

Thanks for providing those details. The P0016 code along with your symptoms definitely aligns with what I experienced. In my A6 case, I initially only replaced the crankshaft sensor, but ended up needing to change both the cam sensor and crank sensor for a complete fix. The constant engine light and cold start issues are particularly telling. These symptoms match exactly what I dealt with, the misfires during acceleration were happening because the engine control unit wasnt receiving accurate timing data for proper engine synchronization. Since your timing chain service is recent, its highly unlikely to be the cause. The reference value errors are almost certainly sensor-related. Based on my experience, I recommend replacing both sensors together. While it costs a bit more upfront (around 520 Euro for both including labor in my case), it prevents having to do the job twice if the other sensor fails soon after. The sensors work as a pair to maintain proper engine synchronization, and when one fails, the other is typically not far behind, especially at your mileage. My mechanic explained that the timing chain service actually puts additional stress on aging sensors, which could explain why issues appeared after your recent maintenance. Have you noticed if the symptoms get worse in wet weather? This was another telltale sign with my sensor issues.

Based on your feedback and my symptoms, I think I'll go ahead with replacing both sensors. Your point about them working as a pair makes sense, and I dont want to risk having to do this repair twice. The timing chain being recently serviced gives me peace of mind that the core timing components are likely fine. Interestingly, now that you mention it, the problems do seem worse in damp conditions. The engine synchronization issues are definitely more pronounced during morning starts when theres higher humidity. The misfires during acceleration have also gotten more frequent lately, which matches what you described about failing sensors. I checked with my regular shop, and they quoted 495 Euro for replacing both the crankshaft and camshaft sensors, including labor, which seems in line with what you paid. Going to schedule the repair for next week. Really appreciate the detailed information about your experience, it helped confirm my suspicions about the sensors being the root cause rather than a more serious timing chain problem.