XT6 Engine Issues: Knock Sensor and Power Problems

Had almost identical symptoms on my 2019 XT5 last summer. With some experience working on engines, I recognized the classic signs of pre-ignition and detonation pretty quickly. The knock sensor was triggering constantly, and the ECU was pulling timing to protect the engine. The root cause turned out to be heavy carbon deposits in the combustion chamber affecting cylinder heads. The deposits were creating hot spots causing pre-ignition. My workshop did a thorough cleaning of the combustion chambers, replaced the knock sensor as a precaution, and adjusted the timing. Total cost was 425€ and took about 6 hours of labor. The piston slap noise I was hearing completely disappeared after the repair. To help diagnose your case better, could you share: Current mileage, Type of fuel you normally use, When you first noticed the symptoms, Whether the smoke is black, white, or blue, Specific error codes from the scanner This will help determine if your issue matches what I experienced and whether a similar repair approach would work. The symptoms you describe are serious and could lead to engine damage if not addressed. Would strongly recommend getting it checked soon rather than continuing to drive with these symptoms.

Last service was at 102000 KM, just 7500 KM ago. My issue appears more concerning than yours, as the smoke is distinctly blue and the engine jerking gets worse at higher RPMs. Scanner shows P0332 and P0325 codes, indicating knock sensor circuit problems. The engine tuning seems way off, especially during acceleration. After reading your experience, I checked my maintenance records and noticed I have been using lower octane fuel recently, which could contribute to the pre-ignition issues youve mentioned. The tips about carbon deposits and cylinder heads inspection are particularly helpful. Could you share how long your fix has lasted without issues returning?

Thanks for sharing those details about your XT6. The blue smoke and increasing jerking at higher RPMs does suggest a more complex issue than what I dealt with in my XT5. The knock sensor codes combined with blue smoke points to possible oil entering the combustion chamber. While my issue was mainly carbon deposits, yours might involve worn valve seals or piston rings. The low octane fuel definitely worsens the pre-ignition situation, making the knock sensors work overtime. To answer your question, my repair has held up perfectly for 15 months now. No ignition timing issues or piston slap have returned. But I strictly use high octane fuel since the repair to prevent carbon buildup. Given your symptoms: Blue smoke indicates oil burning, Multiple knock sensor circuit codes, Worsening jerking at higher RPMs, Relatively recent oil service Your repair might need to go beyond just cleaning and sensor replacement. Would suggest having the cylinder compression tested and checking for oil leaks past the valve seals. The total repair cost could be higher than my 425€ case, but addressing it promptly will prevent more serious engine damage.

Current mileage is 109500 KM. Using mostly 87 octane lately to save money, which was probably a mistake based on your feedback. First noticed the symptoms about 3 weeks ago, starting with minor power loss that has gotten progressively worse. The smoke is definitely blue, especially on cold starts, and gets worse under load. The scanner shows P0332 and P0325 codes, both related to knock sensor issues, plus a P0301 indicating cylinder 1 misfire. Your experience with carbon deposits in the cylinder heads and pre-ignition problems seems similar, though my symptoms appear more severe. Appreciate the detailed breakdown of your repair process. Given my symptoms and the blue smoke, Im concerned this could be more extensive than just carbon buildup. Planning to take it to the shop this week since the engine tuning is clearly off and the jerking during acceleration is getting worse. The information about your 425€ repair cost helps set expectations, though Im prepared it might cost more in my case. Will definitely have them check the knock sensor and combustion chamber deposits. Do you think 6 hours labor time is realistic for my situation?