hello,
i actually have a 2000 prizm and my problem has to do with a rattle sound, like shaking a can of spray paint when the engine is restarted when already warmed up. cold starts are normal regardless of outside air temp. car will start normally with no noise when cold but if it is turned off and restarted when warm it produces a rattle sound for appx
2-3 seconds. the problem is also intermittent as it only does this 50 percent of the time. what is even more confounding is it may or may not rattle after sitting for 10 seconds or 10 minutes, its all random. things to consider are the vehicle is well maintained with 3000 mile oil and filter changes using a synthetic oil. vehicle has 75k miles and was a purchased 3 years ago used with 28k miles while the rattle appeared around 65k miles. i use 5w30 in winter and 10w30 in summer and ive tried every brand filter i can find including toyota and ac/delco but it still rattles. yes, the serpentine belt tensioner has been replaced with the updated unit. any ideas? oil pump going?thanks, py