GM 91174417 Sprocket,Camshaft

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Before you start removing and replacing timing components be very careful because the timing system is complex and errors can result in serious damage to an engine. If you have never done such repairs before, consult with a professional. Start by removing the camshaft cover and intake manifold timing chain cover. Turn the crankshaft so that the key is aligned with a mark on the block while ensuring that the camshaft sprocket marks align with those on the head, and check that the arrow mark on the idler sprocket points up, which means that No. 1 piston is at top dead center (TDC). Remove bolts and nut for adjuster of timing chain tensioner, release tension and remove adjuster. Thereafter, remove each sprocket retainer bolt from intake and exhaust camshafts using a wrench to hold each shaft still. Be careful not to rotate camshafts independently of crankshaft while removing camshaft timing chain and sprockets so as not to damage them. Likewise, remove big timing chain, idler sprocket and crankshaft sprocket by taking off both camshaft cover and timing chain cover then repeat step one until number piston one reaches TDC once again. Get rid of small timing chain then take out camshaft sprockets followed by tensioner as well as guide for this chain. Take off tensioner of timing chain; idler sprocket, timing chain along with crank shaft sprocket. Check all parts for oil or dirt contamination as well damage or excessive wear when inspecting components. Change any worn out or damaged part. For installation match crankshaft's stationary key mark with its corresponding mark on block when installing crank shaft sprocket having match mark facing outwardly towards you. Lubricate bushing of idler sprocket then install it in conjunction with idler sprocket itself. Fit big timing cycle after ensuring that match marks are in line with each other. Lubricate all components release plunger on tensioner and hold it in place. Install timing chain guide, make sure all marks are aligned properly. For small timing chain and camshaft sprockets align the crank shaft sprocket key and arrow mark on idler sprocket as well as knock pins on camshafts. Install small timing chain and sprockets making sure that yellow plates are aligned with arrow mark on idler sprocket whereas dark blue plates should be aligned with arrow marks on the camshaft sprockets while tightening bolts for immobilizing them firmly. Push down the plunger of tensioner after installing the tensioner itself which is then bolted tightly enough. Rotate crank shaft two complete revolutions checking alignment of timing marks while doing so. Lubricate each part using clean engine oil.

If the timing belt is to be replaced, you may need to slide off the crankshaft sprocket and belt guide. If you plan to replace the camshaft oil seal, you should also remove the camshaft sprocket and cover.