Audi Q7 Diesel: Rough Idle and Engine Jerking Issues

I had a similar issue with my 2004 Audi A6 diesel last winter. Having some experience with diesel engines, I recognized the symptoms you described, especially the rough idle and jerking during acceleration. The issue turned out to be a leak in the exhaust system, which was causing incorrect readings from the oxygen sensor. This triggered the check engine light and affected engine performance. The total repair cost was 265 Euro, including parts and labor. My trusted workshop found the leak during a pressure test of the exhaust system. They had to replace a section of the exhaust pipe and a worn-out gasket. After the repair, the rough idle completely disappeared and the engine ran smoothly again. To better assist with your specific case, could you provide: Current mileage on your Q7, Whether you notice any unusual exhaust smells, If you hear any distinct rattling or hissing sounds from the exhaust, Whether the symptoms get worse when the engine warms up The timing of these symptoms can help narrow down whether your issue is similar to what I experienced. The crankshaft sensor you mentioned could also be a possibility, but the symptoms you describe align closely with exhaust system problems I encountered.

Last service was at 124000 KM, current mileage 126263 KM. Thanks for sharing your experience. My symptoms do get worse after the engine warms up. An additional detail I should mention is that I hear a distinct whistling noise from the engine bay, and fuel consumption has increased noticeably. Interesting point about the exhaust system. In my case though, a mechanic checked and confirmed the exhaust is intact. The engine misfire seems more pronounced at higher RPMs, which makes me lean toward either a failing fuel pump or ignition coil problem. The jerking during acceleration is quite severe, almost like the engine is starving for fuel at times. Have you or others experienced similar symptoms specifically related to fuel system components?

Thanks for providing those additional details about your Q7. After reading about the whistling noise and increased fuel consumption, I am even more convinced your issue differs from my exhaust problems. The symptoms you describe, especially the whistling noise and engine starving for fuel, strongly point toward a failing fuel pump. When my A6 had a similar fuel pump issue last year, it exhibited nearly identical symptoms. The fuel pump started making a high-pitched whistle before eventually causing severe performance problems. The rough idle and misfiring at higher RPMs are classic signs of inconsistent fuel delivery. In my case, replacing the fuel pump resolved all these issues: Whistling noise disappeared, Fuel consumption returned to normal, Engine ran smoothly across all RPMs, Misfiring stopped completely The repair cost me 780 Euro including parts and labor. While not cheap, the difference in performance was immediately noticeable. Have you noticed if the problems are worse when your fuel tank is below quarter full? This can be another telling sign of fuel pump issues. If you want to verify before replacing parts, ask your mechanic to check the fuel pressure. Low or inconsistent readings would confirm the fuel pump diagnosis.

I appreciate the detailed response about the fuel pump issue. The symptoms you described match my situation perfectly, especially the part about problems being worse when the tank is low. I actually noticed this pattern last week but didn't connect it to the fuel pump until now. The engine misfire is definitely most noticeable when my tank drops below a quarter, and the whistling gets louder too. I checked with another Q7 owner who had their fuel pump replaced last month, and they quoted a similar repair cost around 800 Euro. I will have my mechanic check the fuel pressure before proceeding with any repairs. The ignition coil and fuel injectors will also need testing to rule out other potential causes, but based on the symptoms you described, the fuel pump seems like the most likely culprit. This starting to make more sense now. Will update once I get the pressure readings and confirm whether the fuel pump needs replacement. Thanks for helping me narrow down the problem.