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Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53015
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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Have a 1999 s420 runs great but will stall at times but

Customer Question

Have a 1999 s420 runs great but will stall at times but restart no problem have a little fuel smell when it stalls
Submitted: 2 months ago.
Category: Mercedes
Expert:  Marty replied 2 months ago.

Hi, it's hard to diagnose an occasional stalling problem. The first thing I would do is get the car connected to the Mercedes Star Diagnosis tester to check for any stored fault codes that may point to the problem. A faulty crankshaft position sensor is the most common cause of occasional sudden stalling. If the car just dies without warning I'd suspect the crank sensor. If the car gives you a little warning before it stalls such as low idle or rough running I would suspect a fault with the fuel pump or with the electronic throttle actuator. Cleaning the throttle body may help if the problem is caused by too low of an idle speed.

Let me know if you have any questions.