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Adjusting Your Vigor's Valves This month, we'll temporarily depart from our "Engine Systems" series and turn our attention to an important and much discussed item of Vigor maintenance—the valve adjustment. The valves let air and fuel into the engine's cylinders, seal the combustion chambers so the air/fuel mixture can be compressed by the piston, and allow the exhaust gases to leave the cylinders following combustion and the power stroke. Vigor engines have four valves per cylinder (two intakes and two exhausts) to improve breathing efficiency for more power at higher speeds.
Valve Clearance The Vigor has a Single Over-Head Cam (SOHC) engine. A single camshaft, rotating at half the speed of the crankshaft and located in the head above the valves, opens and closes the valves. But the camshaft doesn't directly open and close the valves—instead, each lobe of the camshaft operates a rocker arm. See the illustration at right. Each valve is kept closed by a valve spring. The valve spring is attached to the upper end of the valve stem by a valve keeper (not shown) and pushes the valve upward. This keeps the valve face pressed against the valve seat, sealing the opening (called a port). As the camshaft rotates, a lobe will push upward against the rocker arm. The rocker arm pivots on a shaft, so as the cam pushes the rocker arm up on one side, the other side pushes the valve down, causing it to open. As the camshaft continues to rotate, the lobe will rotate away from the rocker arm and valve spring will cause the valve to rise... and close. In the illustration, you'll notice that the rocker arm on the left is not in contact with a cam lobe, so its valve is pushed up by the valve spring. The rocker arm on the right is being pivoted upward by a camshaft lobe, so it pushes its valve down, opening it. Why Adjust the Valves? The space between the top of the valve stem and the face of the rocker arm that contacts the valve stem is called the valve clearance (or valve lash). This distance determines how far the valve will travel when it opens. More importantly, it also determines when the valve opens—and for how long. If the valve clearance is too great (loose), the valve train will chatter and vibrate, eventually causing excessive wear. If it's too small (tight), the valve will spend more time open. This will have two effects: (1) compression will be reduced, because the valves will remain partially open when they should be sealed closed and (2) the valves will overheat and possibly burn. The valves are right there where the action is. Right there where the air/fuel mixture is ignited and combustion takes place. The hottest temperatures in the engine are right there in the combustion chamber. And since a valve transfers heat from its face to its seat, it can only cool itself while it's closed. If it overheats and burns, the valve face will no longer fit snugly against the seat, and a compression loss will result. The burned area of the valve will get worse as time goes on, and the only remedy is an expensive valve job. Adjusting the Valves According to Acura, your Vigor's valve clearance should be checked every 15,000 miles. In practice, every 30,000 miles should be fine, and even then, they may not need adjustment. But it's important to check. One last important point is to adjust the valves only when the engine is cold. Not "cool." Cold. It's best to adjust the valves after the car has been sitting overnight and not driven. Otherwise, the engine metals will still be expanded from the heat and the adjustments won't be Acurate. Let's get started. Removing the Valve Cover To begin, you'll have to remove the valve cover. What follows may sound involved, but as you look at the engine, it'll all become self-evident. This'll take about five minutes. Maybe ten. First, pull the PCV valve out of the valve cover. See photo below left.
To remove the harness cover, remove the three 10mm bolts and lift the cover off. With the cover off, you can move the now-dangling PCV valve and hose out of the way.
Next, we'll work at the front of the engine. Refer to the photo at right. The PCV Breather Pipe connects to the valve cover. Slip the hose clamp back (upper arrow) and disconnect the hose. Push the pipe and hose section away from the valve cover. Then, remove one of the 10mm bolts that hold the Upper Front Engine Cover in place (lower arrow). There's a wiring harness under it. Move the cover and the harness away from the valve cover.
Next, using a 10mm socket, remove the two bolts that hold the ABS fusebox in place (see photo at right). Push the fusebox back away from the valve cover. With all that stuff out of the way, there should be enough room to wiggle the valve cover out once it's loose. Remove the plug wires. Then, use a 10mm socket to remove the six cap nuts that hold the valve cover on. There's a washer/grommet under each cap nut—pry them off and set them aside so they don't fall off and get lost. You'll also notice that the lower rear cap nut has a ground lug attached to it. Next to the cap nut is another 10mm bolt that secures grounding straps. Remove that bolt also and push the wires out of the way. The valve cover is now ready to come off. You'll probably have to give the valve cover a few well placed whumps with a soft-faced hammer to loosen it first.
The layout of the valves is shown in the illustration at left. The right side of the illustration is the front of the car. You'll have to set up the engine properly to adjust each cylinder's valves (next page). Only when the engine is at Top Dead Center (TDC) on the compression stroke of a given cylinder may that cylinder's valves be measured and adjusted. You'll have to reposition the engine for each cylinder.
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