Smart Fortwo Stalling Issue, Camshaft Sensor Alert

Having some experience with engine control issues, I encountered very similar symptoms on my 2013 Smart ForFour. The check engine light came on, and I was experiencing the same stalling problems during idle. After trying basic troubleshooting, I took it to a workshop where they diagnosed the problem using their diagnostic equipment. The ignition timing was off due to a defective encoder wheel on the camshafts. The sensor failure was causing incorrect readings, leading to the engine stalling issues. The total repair cost was 695€, which included parts and labor. After the repair, the car ran perfectly again with no more stalling or starting issues. To better assist with your situation, could you share: Have you had the diagnostic codes read? Are there any unusual noises from the engine? Does the problem occur more when the engine is cold or warm? Have you noticed any changes in fuel consumption? These details would help determine if your issue matches what I experienced with the encoder wheel failure. Keep in mind that while the symptoms sound similar, proper diagnosis is essential as multiple issues can cause similar problems with engine control systems.

Dealt with a similar issue last service at 162272km. Before spending money on a full camshaft sensor replacement, consider getting the engine misfire codes read first. A faulty crankshaft sensor can also cause these symptoms and is typically cheaper to fix. My mechanic did sensor testing which revealed intermittent signal issues, turned out the wiring harness was damaged, not the sensor itself. The repair was much less expensive than initially expected, around 250€ for diagnostics and repair. Recommend checking if the problems get worse at higher RPMs, as this can help pinpoint whether its an ignition timing issue or actual sensor failure. Sometimes cleaning the existing sensors can resolve these symptoms without needing full replacement.

Thanks for sharing your experience with the wiring harness issue. That's actually quite different from what happened with my Smart ForFour. After the initial encoder wheel repair I mentioned, I started experiencing similar symptoms again about 30000km later. The check engine light returned and engine misfires became frequent. This time I had the codes read immediately. Unlike your case, my problem was definitely the camshaft position sensor itself, it had completely failed. The repair was straightforward but more expensive than your wiring fix, costing 420€ for parts and labor. The key difference I noticed was that with the faulty sensor, the engine misfires were consistent at all RPMs, not just during idle. This matches what you mentioned about RPM behavior being a good diagnostic indicator. The stalling got especially bad when the engine was cold. Your point about checking codes first is spot on. With these Smart engines, getting a proper diagnostic reading can save a lot of money and prevent replacing parts unnecessarily. Sometimes what seems like a camshaft sensor problem can be something much simpler, just like in your case with the wiring.

Thanks everyone for the detailed responses. After reading about your experiences, I went ahead and had the diagnostic codes read first, smart move that saved me money! The code showed a crankshaft sensor issue, not the camshaft sensor I initially suspected. Like some of you mentioned, the ignition timing was off due to the faulty sensor readings. The mechanic confirmed the sensor failure by testing the signals at different RPMs. Total repair came to 285€ including the new crankshaft sensor and labor. Car runs perfectly now, no more stalling or starting problems. The repair shop also cleaned the camshaft sensor while they were at it, since it was easily accessible. Really glad I got the proper diagnosis first instead of jumping to conclusions about which sensor needed replacement. Having these symptoms documented by others who went through similar issues helped me better communicate with my mechanic and avoid unnecessary repairs. Definitely recommend anyone with similar stalling problems to start with a diagnostic scan before replacing parts. The actual problem may be different than what you first suspect.