VW Touran Engine Jerking & Smoke: Timing Issues Alert

I had a very similar issue with my 2016 VW Tiguan last year. Having some experience working on VW engines, these symptoms immediately raised red flags about potential detonation problems. The main culprit turned out to be significant carbon deposits in the combustion chamber, which led to pre-ignition and irregular combustion. The workshop performed compression testing and cylinder leakage tests before confirming the diagnosis with a borescope inspection. The fix involved: Complete cleaning of combustion chambers, Replacement of spark plugs, ECU recalibration, Fuel system cleaning Total cost was 425€ for parts and labor. The car has been running smoothly since, with no more jerking or power loss issues. For a more accurate diagnosis of your Touran, could you share: Current mileage, Fuel type and quality you typically use, When the symptoms first appeared, Whether the check engine light is on, The specific error code shown The piston slap noise is often confused with detonation symptoms, so these details would help narrow down the exact cause. Consider having the ignition timing checked as well, since incorrect timing can create similar symptoms and potentially damage engine components if left unchecked.

Thanks for the detailed reply. My Touran was last serviced at 140000km, just about 5000km ago. They did a standard major service including spark plug replacement. I have been using premium 98 octane fuel consistently. The knock sensor error appeared suddenly last week, along with the check engine light. The error code is P0325. The engine feels especially rough during cold starts and when accelerating from low RPMs. Could the recent spark plug change be related to this issue?

Thanks for those additional details. Having experienced a similar situation with my Tiguan, the P0325 error code specifically points to knock sensor circuit malfunction, which explains the rough running and power reduction. Given the recent spark plug replacement during your service, there are a few potential scenarios to consider: 1. The knock sensor might have been disturbed or its wiring harness damaged during the spark plug replacement. This is actually quite common on VW engines due to the tight placement of components in the combustion chamber area. 2. The new spark plugs could be incorrectly gapped or not torqued to proper specifications, leading to pre-ignition issues that trigger knock sensor responses. In my case, after thoroughly checking everything, we discovered that the knock sensor connector had developed corrosion, causing intermittent signal issues. The workshop initially suspected more serious ignition timing problems, but the fix was relatively simple: Cleaning and reseating the knock sensor connections, Verifying spark plug gaps and torque settings, Checking the knock sensor mounting torque The total repair cost was only 120€, much less than initially feared. Given your symptoms match mine almost exactly, I would recommend having these specific items checked before considering more extensive repairs that might affect the cylinder heads or deeper engine components. Have you noticed if the symptoms improve once the engine reaches normal operating temperature?

Thanks for sharing the repair details from your Tiguan experience. Your explanation about the knock sensor circuit makes a lot of sense. To answer your question, yes, the symptoms do improve slightly when the engine is warm, though the jerking during acceleration remains noticeable. I will have the workshop check the knock sensor connections and spark plug specifications first, since that matches the P0325 error code. Since engine detonation and pre-ignition can cause serious damage, I want to get this resolved quickly. I will make an appointment to have them verify the ignition timing and inspect for any wiring issues that could be affecting the knock sensor readings. The 120€ repair cost you mentioned is much more reasonable than I feared. Do you think I should avoid driving the car until it is checked, or is it safe to continue normal use if I avoid heavy acceleration? I want to prevent any potential engine damage from incorrect combustion timing.