VW Jetta Engine Power Loss with Smoke and Jerking

Had the same symptoms on my 2010 VW Passat TSI. The jerking during acceleration combined with power loss pointed to pre-ignition issues caused by carbon deposits in the combustion chamber. The knock sensor was triggering constantly, forcing the ECU to pull timing to prevent engine damage. This created the jerking sensation and drop in power. The smoke likely indicates oil consumption through worn valve seals, which worsens carbon buildup. Required a full combustion chamber cleaning service. The carbon deposits were significant, had completely coated the valves and pistons. This buildup prevented proper fuel atomization and created hot spots causing pre-ignition. The fix involved: Removing intake manifold, Chemical cleaning of valves and ports, Fuel system service, New spark plugs, Resetting fuel trim values After cleaning, switching to higher fuel octane rating helped prevent deposits from returning quickly. This is a common issue with direct injection engines and requires proper maintenance to prevent reoccurrence. Would suggest finding a shop specializing in VW fuel system services, as the cleaning procedure needs specific knowledge and equipment.

Thanks for explaining what solved your pre-ignition issues. The symptoms match exactly what Im experiencing with the piston slap and knock sensor constantly triggering. Interesting that fuel octane made a difference after the repairs. How much did you end up paying for the complete combustion chamber service? Also wondering if youve had any similar problems since the cleaning was done?

Since having the repairs done 6 months ago, the engine knock issues are completely resolved. The cylinder heads and combustion chamber cleaning fixed the problem permanently, no more piston slap or knock sensor warnings. The total service cost was 425€ for removing all carbon deposits. This included the complete cleaning procedure and new parts. The investment was worth it since the engine now runs smoothly without any pre-ignition problems. Switching to higher fuel octane definitely helped maintain the clean combustion chamber. Running premium grade fuel seems to slow down deposit formation significantly. The engine performs noticeably better on higher octane, especially during hard acceleration. The key was finding a qualified shop that properly diagnosed and treated the carbon buildup. Regular fuel system maintenance is essential with these direct injection engines to prevent the issues from returning. So far, following this approach has kept the engine running perfectly.

After struggling with the constant engine knock and power loss issues, I finally took my Jetta to a new repair shop specializing in engine tuning and VW fuel systems. The technician immediately recognized the pre-ignition symptoms and confirmed heavy carbon buildup was causing the problems. The complete service cost me 480€ but solved all the issues. They cleaned out the combustion chamber, replaced the knock sensor, and did a proper fuel system service. No more piston slap or jerking during acceleration. Been running premium fuel since the repairs and the engine performs perfectly, no smoke, no power loss, no check engine lights. Really wish Id switched repair shops sooner instead of wasting time with a mechanic who couldnt properly diagnose the detonation problems. Sometimes paying more for experienced technicians saves money in the long run.