Cracked Fly Wheel
My '89 Accord just began idling like that. It turns out that two of the belts broke yesterday, so maybe your belts are on the verge of breaking. Mine has been idling like that for just a few days before the belts broke.
One of your belts may be loose or in need of belt dressing.
Loose accessory belts (probably alternator or fan). These stop squealing when they get warm. You might need a new belt, or just tightening.
My son's 1997 Passport has the same problem. A friend told him this is usually caused by the air condition compressor belt. If it is one of the other belts causing the noise you should be able to search for help on how to adjust those.
Check your belts for tightness or glazed edges. If the belts are loose, tighten them. If the edges are glazed, either break the glaze with a piece of scotch brite or replace the belts if they are worn.
It could be the presence of water on pulleys causing the belts to slip. If it is persistent then this is a sign of worn-out or misaligned belts.
The belts are becoming worn and need to be replaced, or the fanbelt tensionning device needs adjustment. The only other thing it could be is that one of the things that the belts are driving is becoming seized (AC pump, power steering pump etc); but if everything else is OK then it is most probably the belts being worn out.
Timing Belts need to be changed around 100k miles or every 6 years. These are safe averages. Timing Belts like tires breakdown with age so it is not just a mileage issue.Other indicatons are an engine that runs rough when coming to a stop or idling. Worn timing belt result in trouble codes from the camshaft or crankshaft sensors, causing a dashboard warning light.
It could be the bearing in your tension pulley.
Either your fan belts are going bad or your alternator is going out. If you take a bar of soap and press it against the belts while the car is running, the squealing should stop.
Because the bearing in it has worn out and it is locking up causing the belt to break.
The number of crashes is not affected by the use (or lack thereof) of seat belts. The level of injury however is very significantly increased by the non-use of seat belts.