VW Tiguan TDI Power Loss Due to Cylinder Issues

Had the exact same symptoms on a 2018 VW Passat TDI. Based on some experience with diesel engines, this turned out to be connected to a previous repair where the timing belt was incorrectly tensioned during replacement. The rough running and power loss were caused by the intake manifold getting clogged due to excessive blow-by, which happened because the timing was slightly off. The check engine light came on due to the cylinder pressure issues your mechanic mentioned. Fortunately, since this was a direct result of the previous repair work, the workshop covered all repair costs under warranty. They had to clean the intake manifold and readjust the timing belt tension. The turbocharger was also inspected for damage but was fine. To help diagnose your specific case better, could you share: Current mileage, When was the last timing belt service done, Any recent repairs or maintenance, Are there any unusual sounds, particularly during cold starts, Does the power loss occur mainly at specific RPM ranges The symptoms you describe could point to several issues with the fuel injection system or timing components, but proper diagnostics are essential before jumping to conclusions about major engine work.

Thanks for the detailed reply. My Tiguan just had its annual service last month at 68924km. I do notice a distinct engine knocking sound during cold starts that goes away after warm-up. The power loss is most noticeable between 2000-3000 RPM. Thinking back, this started gradually after a fuel injector replacement about 6 months ago. The spark plug replacement was also done during that service, but the timing belt was never touched since the car is still relatively new. Seems like the intake manifold cleaning might be worth checking into based on your experience.

Thanks for those additional details. Since our situations share some similarities but have different root causes, I should mention that my Passat problem turned out differently than what might be happening with your Tiguan. Given that your symptoms started after the fuel injector replacement, coupled with the cold start knocking, this points more toward a fuel delivery issue rather than the timing-related problems I experienced. The fact that your power loss occurs specifically in the 2000-3000 RPM range is particularly telling. In my case, after further investigation, we discovered that while the timing belt seemed to be the culprit initially, the real issue was connected to carbon buildup affecting the fuel injector spray pattern. The workshop had to remove and clean all fuel injectors, as one was partially clogged, causing uneven cylinder pressure. Since youve already had injector work done, I suggest having them check: Fuel injector spray patterns and timing, Fuel pressure at the rail, Carbon deposits in the intake ports, Turbocharger wastegate operation in that specific RPM range The repair for my Passat ultimately involved cleaning the intake system and replacing two fuel injectors that showed irregular spray patterns. The head gasket was inspected but found to be fine. Total repair time was about 8 hours.

Thanks everyone for the insights. After getting the car checked again, it turns out my case was quite different from the Passat issue. The mechanic found the new fuel injector from 6 months ago was actually faulty, causing uneven fuel distribution which led to the engine knocking during cold starts. The camshaft position sensor was also showing intermittent errors, contributing to the power loss in that specific RPM range. Good news is the turbocharger and intake manifold are clean and functioning properly, so no major engine work needed. Total repair costs came to 980€ including: Replacement fuel injector under warranty, New camshaft sensor, Diagnostic time, System cleaning and testing The car runs perfectly now with no more cold start issues or power loss. Fuel consumption is back to normal too. Really glad I got that second opinion before proceeding with more extensive repairs.