Smart Forfour Exhaust Flap Failure Causing Loud Noise

Had the same issue with a 2008 Smart ForTwo CDI. The symptoms match exactly what you describe, loud cold starts and error codes related to exhaust components. The flap motor was indeed the root cause. The actuator that controls the exhaust valves had failed, leaving the flap stuck in one position. This is actually a common failure point in these engines as the exhaust system components face harsh conditions. The repair involved replacing both the flap motor and the associated control unit. It was not a quick fix, the entire exhaust system needed inspection as the stuck flap had created some exhaust blockage over time. The mechanic also found carbon buildup around the valve mechanism. This is a serious issue that needs addressing promptly as: It affects engine back pressure, Can lead to reduced performance, May cause additional exhaust system damage if left unchecked, Could trigger more error codes over time The repair requires specific diagnostic equipment to properly calibrate the new flap motor. Would strongly recommend finding a shop familiar with Smart vehicles, as proper installation and programming is crucial for the exhaust components to function correctly.

Thanks for sharing your experience. I have almost the same exhaust flap issues with my Smart Forfour right now. The symptoms you described match perfectly, loud noise and error codes. Just curious, do you remember the total repair cost for the flap actuator and control unit replacement? Also, have you experienced any other exhaust system problems since getting it fixed? Want to know what to expect with mine before heading to the shop.

The exhaust flap repair worked out perfectly on my Smart ForTwo. Total cost came to 190€ for fixing the defective flap motor and getting everything calibrated properly. The repair has held up great, no more error codes or loud noises since the fix. The exhaust valves are working as they should now, with smooth operation during both cold starts and regular driving. Engine performance returned to normal once the exhaust system was working correctly again. The mechanic did a thorough job checking the entire exhaust setup while doing the repair. Just make sure whoever works on it knows how to properly calibrate the new flap motor components. A proper diagnosis and repair of the exhaust flaps really makes a difference in how the car runs. Mine has been trouble-free for months now with no signs of the previous issues returning. The investment was worth it to prevent further exhaust system complications. Better to address these problems early before they cause more extensive damage.

Finally got my Smart Forfour fixed yesterday after dealing with that annoying exhaust flap issue. Found a specialist mechanic who knew these cars inside out. The repair confirmed exactly what was discussed, failed flap actuator causing the loud exhaust noise. Total bill came to 210€, slightly more than expected but included a full exhaust system inspection. The mechanic showed me the old actuator which was completely seized up. The whole job took about 3 hours since they had to clear some exhaust blockage that had built up around the faulty flap. They also reprogrammed the new actuator to work properly with the car's computer. Car runs perfectly now, no more error codes and the exhaust noise is back to normal. Cold starts are quiet again and engine performance feels much better. Definitely worth getting it sorted by someone who knew what they were doing. Thanks for the helpful advice. Would have spent way more time and money trying to diagnose this without the forum input about the exhaust components.