Smart ForFour Cold Start Issues: Bad Injector Symptoms

I had a very similar issue with my 2018 Smart Fortwo. As someone with some hands-on experience working on fuel injection systems, the symptoms you describe sound familiar. My car showed identical hard starting problems and rough running when cold. The engine misfire was particularly noticeable during the first minute after a cold start. After running a proper injector test at my regular workshop, they confirmed a faulty fuel injector was causing inconsistent fuel delivery. The repair involved: complete fuel injector removal and testing, replacement of one defective injector, full system pressure check, computer reset and adaptation. Total cost came to 515€ including parts and labor. Since the repair, cold starts have been perfect and the rough running completely disappeared. Before you proceed with repairs, it would help to know: Does the check engine light come on? Do you notice any smoke from the exhaust during cold starts? Have you already checked the fuel pressure? What is your current mileage? These details would help confirm if your fuel system issues match what I experienced with my Smart. If the symptoms align, having the injectors properly tested would be a good first step.

Thanks for the feedback. My last service was 2 months ago at 75510 KM. The check engine light does flash occasionally during cold starts. I notice blue-ish smoke from the exhaust, especially on those really tough morning starts. Haven't checked the fuel pressure yet, as I lack the proper testing equipment. I appreciate the detailed breakdown of your repair process. Having the injector test done professionally sounds like a sensible next step, especially since the symptoms match so closely. The fuel rail inspection and injector cleaning might be worth considering too, given how similar our hard starting issues seem to be. Was your repair done under warranty? Mine might still be covered since the car is relatively new.

Thanks for those extra details. It does sound remarkably similar to what I experienced with my Smart. The blue smoke and flashing check engine light during cold starts are exactly what I dealt with before getting my fuel injection system sorted. I did check my warranty coverage, but since my car was just over 3 years old at the time, I had to cover the repair costs myself. With your 2020 model, you should definitely check your warranty status. Most Smart fuel system components are covered under the basic warranty if you are still within the time and mileage limits. After my repair, I learned that a rough idle and hard starting combined with blue smoke often indicates the cold start injector is dumping too much fuel into the cylinder. The excess fuel causes incomplete combustion during the cold start phase. The flashing check engine light typically means the engine control unit is detecting these fuel delivery issues. A quick tip from my experience: While waiting for the repair, try cranking the engine for about 5 seconds before actually starting it. This helped prime my fuel system and made cold starts a bit more manageable. Just remember this is a temporary workaround, not a fix for the underlying fuel injection problem.

Thanks everyone, wanted to follow up on this thread and share what happened with my Smart. Took it to the dealer yesterday since I confirmed I still have 6 months left on the warranty. The diagnosis confirmed what you all suggested about the fuel injection system. They found the cold start injector was definitely causing the fuel delivery problems. Their tests showed irregular spray patterns and they could replicate my hard starting issues easily. The dealer performed: Full injector cleaning service, Replacement of the faulty injector, Computer system reset, Test drive to confirm fix Best part, everything was covered under warranty. The rough idle is completely gone now and cold starts are smooth as new. No more blue smoke or check engine warnings either. For anyone searching the forum later with similar symptoms, getting the injector properly tested was definitely the right call. The combination of hard starting, rough idle and blue smoke seems to be a clear sign of fuel injection problems in these engines.