Engine Mechanical problem
1999 Toyota Carina 4 cyl Two Wheel Drive Automatic 85000K miles
the engine of the car a 1800cc 7A4E engine made loud tapping noises. On performing a visual check I noticed that the pulley belts were turning by themselves (like a millimeter a second when the sound was being made. On trying to start the engine the battery was low and what seemed apparent to me was that the engine had been trying to turn itself, even though it was off. On jump starting the engine turned on smoothly and has done approx. 20km after the incident. What would be the cause of the noise, and what are its probable consequences.