So your Toyota is due for its timing belt.  Your owner’s manual states you should replace the timing belt at 105k for most models produced after 1996.    The timing belt has a big job to do it must keep the camshafts spinning in exact time with the crank shaft.  This is so the valves open up at the proper time in the combustion cycle in time with air and fuel coming in, compression and spark exploding the mixture and the exhaust valves opening up to release the exhaust gas.  At the same time the timing belt needs to turn the water pump and be able to automatically adjust.  Over time the rubber in the belt stretches out and the automatic tensioner cannot adjust accordingly.  A worn or stretched timing belt can cause poor performance and a decrease in fuel economy.   With Toyota, there is less risk of additional engine damage because the only Toyota interference engines are the older 1.5L Tercel, 2.4L Pickup and 1.8L Camry and Corolla engines. Apparently, Toyota engineers were more generous with combustion chamber clearances than Honda engineers.

 

When should you replace the timing belt on your Toyota?  According to Toyota: If your vehicle is a 1999 model year or newer and is equipped with a timing belt, you should replace it every 90,000 miles or six years, whichever comes first.  For all other Toyota vehicles equipped with a timing belt, we recommend that the timing belt be inspected with the other drive belts at 60,000 miles or four years, whichever comes first, and every 15,000 miles thereafter and replaced as necessary. Because the costs involved with inspecting the timing belt may be similar to those of having it replaced, many customers may find it more cost effective to replace the timing belt at 60,000-mile intervals.