Lexus IS Engine Knocking

Evening. I've got a 2020 Lexus IS with a gasoline engine that's developed a nasty habit. At 30,158 km, it's started knocking fiercely under load – especially when accelerating. Feels like pre-ignition. Alongside the knocking, I'm getting reduced engine power, the car jerks when I accelerate, and there's a puff of smoke out the back when it happens. I've hooked it up to a code reader, and there's an error stored. I'm suspecting it might be deposits in the combustion chamber. Anyone else experienced something similar with their IS, or perhaps another vehicle?

4 comment(s)

Greetings. Your description bears a striking resemblance to an issue I encountered with my previous vehicle, a 2016 BMW 3 Series. It exhibited analogous symptoms, including audible knocking, diminished power output, and irregular acceleration patterns. The diagnostic process revealed analogous error codes pertaining to combustion irregularities. The root cause, as determined by the certified BMW technicians, was attributed to carbonaceous deposits accumulating within the combustion chambers. Could you please elaborate on the specific error code retrieved from your diagnostic tool?

Thanks for the swift response! The error code is P0300, which is a generic random/multiple cylinder misfire code. The Lexus service manual points towards a few potential causes, but the deposits in the combustion chamber seem most likely given the symptoms. Did the BMW technicians mention anything specific about how the deposits formed in your case, or what the best course of action was to rectify the issue?

Affirmative. The BMW technicians indicated that the carbonaceous deposits were a consequence of the direct injection system, a common attribute shared with your Lexus IS gasoline engine. The absence of port fuel injectors to cleanse the intake valves and combustion chambers contributes to deposit accumulation over time. Considering the error code and your preliminary assessment, it would be prudent to seek counsel from a qualified Lexus service center. They possess the requisite expertise and specialized tools to conduct a thorough diagnostic evaluation and administer appropriate remediation strategies, which may include chemical induction treatments or, in more severe instances, physical removal of the deposits.

Appreciate the advice; you've pretty much confirmed my suspicions. I booked it into a reputable independent Lexus specialist; they scoped the cylinders and found significant carbon buildup. They performed a chemical clean, and the issue is now resolved. Total cost was 425€, which I was happy with. Thanks again for sharing your experience!

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