The timing system is complex, and severe engine damage will occur if mistakes are made. Only attempt this procedure if you are highly experienced with this type of repair; if unsure, consult an expert. Double-check all work to ensure everything is correct before starting the engine. This procedure is difficult and requires special tools, so read through all necessary information and obtain the required tools beforehand. New camshaft sprocket bolts must be purchased ahead of time. Begin by disconnecting the cable from the negative terminal of the battery, removing the engine cover, and the air filter housing. Loosen the right front wheel lug nuts, raise the front of the vehicle, and support it securely on jackstands while applying the parking brake and blocking the rear wheels. Remove the wheel and the inner fender splash shield, along with the under-vehicle splash shield. Remove the drivebelt and drivebelt tensioner, followed by the upper timing belt cover bolts and cover. If working on a vehicle with a manual transaxle, remove the transaxle front mount. Set the engine at TDC for the number one cylinder and install a flywheel/driveplate locking tool. Remove the crankshaft pulley and the lower timing belt cover, then install a special tool to lock the camshaft adjuster sprockets in place. Rotate the timing belt tensioner clockwise until a lock pin can be inserted, then remove the idler pulley center bolt and idler pulley, replacing the idler pulley bolt. If reusing the belt, mark it with an arrow indicating direction of travel and match marks from the belt to the sprockets for easy realignment. Remove the timing belt and tensioner, always replacing the tensioner bolt with a new one during reassembly. To remove the camshaft adjuster sprockets, loosen the special tool, then rotate the crankshaft 60 degrees counterclockwise before TDC. Remove the valve cover and rotate the camshafts until the slots are parallel with the cylinder head, then install a special tool or a metal bar into the slots. The camshaft adjuster sprockets can now be removed if necessary; hold the hex area of the camshaft securely with a wrench, remove the outer closure plugs, and then the camshaft adjuster sprocket bolts, replacing them with new ones. Check the belt for oil or dirt and inspect for visible defects, ensuring the tensioner and idler pulley turn smoothly. Clean the timing belt area, install the camshaft sprocket(s) with new bolts, and lock the camshaft adjuster sprockets in place with a special tool. Tighten the adjuster sprocket bolts securely without using the special tool to hold the camshafts, as this could cause damage. Install and tighten the adjuster sprocket closure plugs, then remove the special tool. Install the timing belt tensioner and idler pulley with new bolts, tightening them securely. Slide the crankshaft sprocket onto the end of the crankshaft, ensuring alignment with the TDC marks. Cover half of the timing belt with tape, thread it through the engine mount bracket, and then remove the tape. Verify the crankshaft timing mark is at the 6 o'clock position, align the camshaft sprockets with the special tool, and install the timing belt. Rotate the tensioner clockwise until the locking pin can be removed, then turn the crankshaft slowly through two complete revolutions, ensuring the timing marks are aligned. If they are not aligned exactly, repeat the timing belt installation procedure, and do not start the engine until certain that the timing belt is installed correctly to avoid serious engine damage. The remainder of the installation follows the reverse order of removal.
Posted by GMPartsGiant Specialist 
