Smart ForFour Engine Issues Linked to Air Temp Sensor

I dealt with a very similar issue on my 2017 Smart Fortwo. With some experience working on cars, I can relate to these engine issues you are describing. The symptoms were nearly identical, rough running engine, reduced power, and the check engine light. The air temperature sensor was indeed the problem in my case. The faulty temperature reading was causing the engine management system to supply incorrect fuel mixtures. Had it checked at a workshop where they confirmed the intake air temperature sensor was defective. Total repair cost was 155€, including diagnostics and replacement. After fixing it, the engine ran smoothly again and power was fully restored. To better assist with your specific case, could you share: Have you had the error code read? Does the problem get worse when the engine is cold or hot? Are there any other warning lights besides the check engine light? Have you noticed any changes in fuel consumption? This information would help determine if your air sensor issue matches what I experienced with my Smart.

Thanks for sharing your experience. My situation matches closely with what you described. Just had a diagnostic test done that showed error code P0113, specifically pointing to the IAT sensor. The engine issues are most noticeable during cold starts and fuel consumption has increased by about 15%. Latest service was at 59000 KM where they did not detect any sensor problems yet. The workshop suggested a full diagnostic check to rule out related temperature reading issues before replacing the air sensor. Hearing your successful repair outcome is encouraging. Will schedule the repair soon since these engine issues are impacting daily driving.

Thanks for the update. The P0113 code you mentioned matches exactly what I encountered with my Smart Fortwo, specifically indicating a high-circuit issue with the intake air temperature sensor. The increased fuel consumption and cold start issues are classic symptoms. In my case, the faulty air sensor was causing incorrect temperature readings, making the engine computer adjust the fuel mixture incorrectly, especially during cold starts. The diagnostic tool readings from your workshop align with my experience. While my sensor failed around 65000 KM, these components can deteriorate at different rates. Since your latest service showed no issues at 59000 KM, this suggests a relatively rapid sensor degradation, which is not uncommon. My advice based on personal experience: proceed with the air temperature sensor replacement. The comprehensive diagnostic check your workshop suggested is reasonable, but given the matching error code and symptoms, the intake air sensor is likely the root cause. Would you mind sharing the results once you get it fixed? Be sure to note if the cold start behavior improves immediately after the repair, as this was the first positive change I noticed with my Smart.

Thanks everyone for the helpful input. After considering all the feedback and given how closely my symptoms match others experiences, I decided to go ahead with the repair. Just got back from the workshop where they completed a full car diagnostics session and replaced the intake air temperature sensor. The total cost came to 180€ including parts and labor. Happy to report the engine is running smoothly again. Cold start behavior improved immediately and power delivery is back to normal. The car sensor replacement resolved all the issues I was experiencing. Will monitor the fuel consumption over the next few weeks, but initial signs are promising. The temperature reading values from the new sensor show normal ranges according to the final diagnostic scan. Really appreciate all the responses that helped confirm my initial suspicion about the air sensor being the culprit. This forum continues to be an invaluable resource for troubleshooting car issues.