Smart Roadster Engine Jerks and Smokes During Acceleration

Having owned a Smart Fortwo (2003) with similar issues, I can share some relevant experience dealing with this specific problem. From what you describe, I dealt with almost identical symptoms, jerky acceleration, smoke, and reduced power. After taking it to my trusted workshop, they discovered significant deposits in the combustion chamber causing detonation issues. The piston slap and irregular combustion were triggering the knock sensor, which then adjusted timing to compensate. The fix involved: Cleaning the cylinder heads, Adjusting fuel mixture, Replacing spark plugs, Using higher fuel octane rating afterwards Total cost was 425€ for the complete service, which resolved the issues completely. To better assist with your case, could you provide: Current mileage, Type of fuel you typically use, When was the last spark plug change, Does the smoke have a specific color, Any recent changes in driving patterns These details would help determine if your Roadster is facing the same underlying problem. The symptoms strongly suggest combustion chamber deposits, but confirming these points would help rule out other potential causes.

Thanks for sharing that experience with your Fortwo. The smoke from my Roadster is indeed grayish, and I use regular 95 octane fuel. My latest service was 3 months ago at 123104 KM. The mechanic didnt mention any combustion-related concerns then. The engine knock symptoms only started last week, but have gotten worse even with careful driving. Based on your feedback about detonation issues, I will try switching to higher fuel octane first to see if that helps with the ignition timing problems before booking another service appointment.

Thanks for those additional details. The similarities between our cases are striking, my Fortwo showed the same rapid deterioration of symptoms within a short timeframe. While switching to higher octane fuel might temporarily help with engine knock, my experience suggests this is likely masking a deeper issue. The fact that symptoms appeared so suddenly after a recent service points toward potential problems with engine tuning parameters or a failing knock sensor. In my case, even after initially switching to premium fuel, the problems returned within weeks. The cleaning of cylinder heads and recalibration of the engine management system were what ultimately fixed it. Keep in mind that Smart engines are particularly sensitive to carbon deposits and incorrect fuel mixtures. The grayish smoke combined with knock sensor activation typically indicates incomplete combustion, which matches what I experienced before the repair. Would strongly suggest not waiting too long before getting it checked, continuing to drive with these symptoms could lead to more extensive engine damage, just as I learned with my Fortwo. The good news is that if caught early, the fix should be straightforward. The full service might cost less than what I paid if caught before serious carbon buildup occurs.

Thanks for the comprehensive information about your Fortwo experience. Knowing my Roadster has such similar symptoms is quite helpful. Current stats for my car: Mileage: 123104 KM, Using regular 95 octane fuel, Recent service 3 months ago, Grayish smoke, Normal daily driving pattern The rapid onset of pre-ignition issues matches what you described. Have switched to higher octane fuel today to test if it helps with the engine knock, but your point about this being a temporary fix makes sense. Dont want to risk further engine damage by delaying proper repairs. Based on your description of carbon deposits causing detonation problems, I will book a service appointment this week. Will request they specifically check the cylinder heads, knock sensor, and engine tuning parameters. Better to address it now before the repair costs increase. Thanks again for sharing the details about your experience, really helped clarify what might be happening with my engine.