I hope this helps. I've included the instructions for resetting the tensioner, but I'd suggest you replace it. They are not too expensive and they have a fairly high failure rate in my experience. Before this part, you will need to pull the alternator and the engine support bracket. These instructions are from the service manual, you can ignore the "special tools" as most of the are just sockets. You WILL need the crank puller.
<a href="http://imgur.com/8f6sFHY"><img src="http://i.imgur.com/8f6sFHY.gif" title="source: imgur.com" /></a>
<> Crankshaft Pulley Removal
<a href="http://imgur.com/5Y3yiMG"><img src="http://i.imgur.com/5Y3yiMG.gif" title="source: imgur.com" /></a>
CAUTION: Use only the specified special tools, or a damaged pulley damper could result.
Use special tools MB990767 and MD998715 to remove the crankshaft pulley from the crankshaft.
<> Timing Belt Removal
<a href="http://imgur.com/4GxGLTc"><img src="http://i.imgur.com/4GxGLTc.gif" title="source: imgur.com" /></a>
CAUTION: Never turn the crankshaft counterclockwise.
Turn the crankshaft clockwise to align each timing mark and to set the number 1 cylinder to compression top dead center.
If the timing belt is to be reused, chalk an arrow on the flat side of the belt, indicating the clockwise direction.
Loosen the center bolt of the tensioner pulley, then remove the timing belt.
Installation Service Points
>>A<< Auto-Tensioner Installation
<a href="http://imgur.com/gMSbQJi"><img src="http://i.imgur.com/gMSbQJi.gif" title="source: imgur.com" /></a>
While holding the auto-tensioner with your hand, press the end of the pushrod against a metal surface (such as the cylinder block) with a force of 98 - 196 N (22 - 44 lb) and measure how far the pushrod is pushed in. Standard value: Within 1 mm (0.04 inch)
A: Length when no force is applied
B: Length when force is applied
A - B: Amount pushed in
If it is not within the standard value range, replace the autotensioner.
CAUTION:
Place the auto-tensioner perpendicular to the jaws of the vice.
If there is a plug at the base of the auto-tensioner, insert a plain washer onto the end of the auto-tensioner to protect the plug.
<a href="http://imgur.com/WPs3poZ"><img src="http://i.imgur.com/WPs3poZ.gif" title="source: imgur.com" /></a>
Place two blocks in a vice as shown in the illustration, and then place the auto-tensioner in the vice.
CAUTION: Never compress the pushrod too fast, or it may be damaged.
Slowly compress the pushrod of the auto-tensioner until pin hole A in the pushrod is aligned with pin hole B in the cylinder.
Insert the setting pin into the pin holes once they are aligned.
<a href="http://imgur.com/1xEeSRj"><img src="http://i.imgur.com/1xEeSRj.gif" title="source: imgur.com" /></a>
NOTE: If replacing the auto-tensioner, the pin will already be inserted into the pin holes of the new part.
CAUTION: Do not remove the setting pin from the auto-tensioner.
Install the auto-tensioner to the engine.
>>B<< Timing Belt Installation
Align the timing marks on the camshaft sprockets with those on the rocker cover and the timing mark on the crankshaft sprocket with that on the engine block as shown in the illustration.
<a href="http://imgur.com/zUXsi61"><img src="http://i.imgur.com/zUXsi61.gif" title="source: imgur.com" /></a>
CAUTION: The camshaft sprocket (right bank) can turn easily due to the spring force applied, so be careful not to get your fingers caught.
Install the timing belt by the following procedure so that there is no deflection in the timing belt between each sprocket and pulley.
Crankshaft sprocket
Idler pulley
Camshaft sprocket (Left bank)
Water pump pulley
Camshaft sprocket (Right bank)
Tensioner pulley
Turn the camshaft sprocket (Right bank) counterclockwise until the tension side of the timing belt is firmly stretched. Check all the timing marks again.
<a href="http://imgur.com/XVC3riK"><img src="http://i.imgur.com/XVC3riK.gif" title="source: imgur.com" /></a>
Use special tool MD998767 to push the tensioner pulley into the timing belt, then temporarily tighten the center bolt.
Use special tool MD998769 to turn the crankshaft 1/4 turn counterclockwise, then turn it again clockwise until the timing marks are aligned.
<a href="http://imgur.com/jbEWike"><img src="http://i.imgur.com/jbEWike.gif" title="source: imgur.com" /></a>
CAUTION: When tightening the center bolt, be careful that the tensioner pulley does not turn with the bolt.
Loosen the center bolt of the tensioner pulley. Use special tool MD998767 and a torque wrench to apply the tension torque to the timing belt as shown in the illustration. Then tighten the center bolt to the specified torque. Standard value: 4.4 Nm (39 in. lbs.) Timing belt tension torque>
<a href="http://imgur.com/E1l8vJ2"><img src="http://i.imgur.com/E1l8vJ2.gif" title="source: imgur.com" /></a>
Tightening torque: 48 ±6 Nm (36 ±4 ft. lbs.)
Remove the setting pin that has been inserted into the autotensioner.
Turn the crankshaft clockwise twice to align the timing marks.
Wait for at least five minutes, then check that the autotensioner pushrod extends within the standard value range. Standard value (A): 3.8 - 5.0 mm (0.15 - 0.20 inch)
If not, repeat the operation in steps (5) to (9) above.
Check again that the timing marks of the sprockets are aligned.
