Smart ForFour Misfires Causing Rough Running and Power Loss

Had similar issues with my Smart Fortwo (2015, gasoline) last winter. The symptoms matched exactly, rough idle, engine misfiring, and sluggish throttle response when accelerating. After inspection, it turned out the fuel injector was clogged and not delivering proper fuel spray pattern. This caused incomplete combustion and created the misfire condition. The repair involved removing and cleaning all injectors, but one was damaged beyond repair and needed replacement. This is typically a serious issue that should be addressed promptly. Running the engine with faulty injectors can lead to catalytic converter damage and increased fuel consumption. The repair process required specialized equipment to test injector spray patterns and proper cleaning tools. While waiting too long caused extra work in my case, catching these symptoms early usually means a simpler fix. Key warning signs include: Engine running rough at idle, Drop in power during acceleration, Check engine light with misfire codes, Uneven engine sound, Poor fuel economy The spark plugs were also replaced during the repair since they showed carbon buildup from the poor combustion. Getting this fixed restored proper throttle response and smooth engine operation. This type of repair typically requires a qualified technician with proper diagnostic equipment, not something for DIY unless highly experienced with fuel systems.

Thanks for sharing your experience with the fuel injector and spark plug issues. I had nearly identical symptoms with my Smart Forfour last summer. The check engine light came on and I noticed combustion misfire problems especially during acceleration. The ignition coils ended up being the root cause in my case. Do you remember roughly how much you paid for your repair? Just wondering how it compares. Also curious if youve had any related issues pop up since getting it fixed?

Thanks for asking about the costs. After seeing my mechanic about the combustion misfires in my Smart Fortwo, I can report the issue was completely resolved. The repair bill came to 515€ for replacing the faulty fuel injector. Since the fix, the throttle response is perfect and the engine runs smoothly again. No cylinder misfires or check engine lights have appeared in the months following the repair. The investment was worth it as the car performs like new, especially during acceleration. Interesting that your ignition coils were the culprit, fuel delivery and spark issues can show similar symptoms. Good fuel injectors need proper spark from the ignition system to work efficiently, so both components are crucial for preventing misfires.

I took my Smart Forfour to a certified mechanic last week after reading these responses. The diagnostic test confirmed cylinder misfires caused by worn ignition coils. Total repair cost was 380€ including parts and labor. The mechanic found two failing coils and replaced all spark plugs as preventive maintenance. The engine misfiring symptoms disappeared immediately after the repair. Throttle response is now crisp and the check engine light is off. Really glad I addressed this promptly. The car runs like new and the repair cost was lower than I feared. Found a trustworthy shop too, they explained everything clearly and completed the work same day. No issues since the fix. Will definitely return to this mechanic for future service needs.