Q: RPMs drop to zero (typically on acceleration). Usually come back up and belt squealing sound is heard; sometimes engine shuts down

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This has happened every other year or so (usually early winter) since I got this car 8 years ago. Each time the check engine code read out a cam shaft position sensor malfunction. This time, no code was reading out. I got my spark plugs replaced and that didn't relieve the symptom. I assumed this was the cam shaft position sensor again, so I had that replaced. Drove off from the mechanic, and the symptom was still present: periodic drop in RPMs typically while accelerating (or when I felt the gears shifting). The first one that occurred after leaving was a complete drop to zero; then when I pressed the accelerator, the RPMs came back up and the belt was making a loud squealing noise (not unusual, as this sound has happened consistently for many years and my mechanic noted that the belt was fine, and would put lube on it to keep from sqealing). Note: mechanic inspected belt and said that it wasn't worn, but it had power steering fluid on it and they wiped it off.

My car has 113000 miles.
My car has an automatic transmission.

Hello. We will be happy to assist you. You most likely have a stuck pulley along the serpentine belt routing. My first guess would be the power steering pump because it is leaking fluid so that is the component I would investigate first when initially diagnosing your vehicle. The belt should be removed and the pulley should be spun by hand to determine if they have any abnormally high resistance. High resistance indicates that the bearing inside of the pulley is bad and that pulley should be replaced. The squeaking sound you mentioned is likely the belt slipping across the stuck pulley which is not spinning as fast as it should be. Usually an engine will still be able to turn the belt system to an extent. However the stuck pulley will not be able to spin as fast as the other components so a squeaking sound is heard from the stuck pulley because of the belt slipping across that slow pulley. Anytime that a belt is squealing that is a sure sign that the belt is not okay. The belt is either contaminated, a pulley is bad or the belt needs adjusting. A technician should also scan your vehicle’s computer again to see what codes maybe present. Please keep in mind that here at YourMechanic we specialize in such diagnosis and repair.

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