Smart Roadster Stalling: Fuel Tank Vent System Fix

Had the same symptoms on a Smart Forfour from 2006. The check engine light triggered due to a faulty activated charcoal filter system. The air flow was restricted, causing irregular fuel tank pressure readings and engine stalling issues. Initial leak detection tests confirmed problems with the purge valve and charcoal canister. The mechanic found that the charcoal filter was completely saturated and not properly filtering fuel vapors. This explains both the fuel smell and the stalling, as the system affects the fuel-air mixture at idle. The repair required replacing the entire charcoal canister assembly and purge valve to restore proper fuel efficiency and system pressure. While not immediately dangerous, running with a defective system can lead to increased emissions and potential fuel system damage if left unchecked. The fix also included cleaning the throttle body and checking all related vacuum lines for potential leaks. After replacement, the pressure sensor readings returned to normal range and the stalling issue was completely resolved. Would suggest having a professional run a proper diagnostic test focusing on the EVAP system components. The symptoms match a typical charcoal filter failure pattern.

Thanks for sharing your experience. This matches exactly what happened with my Roadster. After reading your post, I went ahead and had the EVAP system components checked. Just like in your case, the emission control system was failing due to a saturated charcoal filter. Would you mind sharing how much the repair cost in your case? Also curious if you had any related issues pop up since the fix. My mechanic mentioned something about checking the fuel tank pressure sensor while they are at it, but not sure if that is really necessary.

Following up on your questions, glad to hear you got the EVAP system checked out. The repair set me back 275€ for the defective activated charcoal filter replacement, which completely resolved the system failure. Looking back, it was money well spent since the check engine light never came back. The fuel tank ventilation system leak was fixed during the same service, and I have not experienced any related issues in the months since. The engine runs smoothly at idle now, with no more stalling problems or fuel odors. Regarding the pressure sensor, in my case, it turned out to be working fine once the charcoal filter was replaced. The irregular readings were caused by the saturated filter disrupting normal air flow. Unless your mechanic detected specific sensor issues during leak detection tests, replacing it might be an unnecessary expense.

Thanks for the helpful advice. I wanted to share how my repair went. Took it to a new mechanic who specializes in fuel system repairs. The leak detection test confirmed the charcoal filter was completely clogged, just as suggested here. Total repair came to 320€ including labor. They replaced the charcoal canister and checked the entire emission control system. The fuel tank pressure readings normalized right after, and the check engine light finally cleared. No more stalling issues at idle. The mechanic did a thorough job explaining everything and showed me the old saturated filter. Definitely worth finding a specialist who knows these systems well. The car runs so much better now, no more fuel smell and perfect idle. Really glad I got this sorted before it caused any additional problems with the fuel system. For anyone facing similar symptoms, get the EVAP system checked first. Could save you from more expensive repairs down the road.