For 1990-2009 cars

### Engine Construction

The engine is a four cylinder in-line, four stroke gasoline unit with a Double Overhead Cam (DOHC) valve mechanism arranged for V-type valve configuration.

The DOHC is mounted over the cylinder head and is driven by the crankshaft through two timing chains. In this configuration there are no push rods and no rocker arms provided in the valve train system.

### Cylinder Block

The cylinder block is an aluminum casting with four cast iron cylinder sleeves. The cylinder block has four in-line cylinders which are numbered 1 through 4 starting from the crankshaft pulley. The cylinder block contains coolant jackets through which coolant flows around the cylinders, to cool the cylinder block and maintain a constant operating temperature. The lower crankcase of the cylinder block is also an aluminum casting with cast iron inserts at the main bearing locations. The lower crankcase runs the entire perimeter of the cylinder block.

### Crankshaft

The crankshaft is nodular cast iron and is supported by five main bearings. The crankpins of cylinders 1 and 4 are 180 degrees from the crankpins of cylinders 2 and 3. The crankshaft is counterbalanced by the flywheel, the crankshaft balancer and eight counterweights cast into the crankshaft. Oil holes run through the center of the crankshaft to supply oil to the connecting rods, bearings, pistons and other components. The end thrust load is taken by the thrust washers installed at the center number three bearing journal. The main bearings are of the precision insert type. The front of the crankshaft incorporates a sprocket which drives the oil pump through a sprocket and chain.

### Connecting Rod and Piston

Each piston is cast aluminum alloy and has two compression rings and one oil ring. The piston rings are of a low tension type to reduce friction. The top compression ring is plated with chromium for abrasion resistance. The second compression ring is gray iron. The oil ring is a 3-piece spring construction, consisting of two rails and one spacer.

The piston pin is offset 0.5 mm (0.02 in) toward the thrust side. This allows a gradual change in thrust pressure against the cylinder wall as the piston travels through the bore. The connecting rods are forged steel, heat treated and shot peened. Piston pins are chromium steel and have a full floating fit in the pistons and in the connecting rods. The connecting rod bearings are of the precision insert type.

### Oil Pump

The oil pump is bolted to the bottom of the lower crankcase. A sprocket on the front of the oil pump is driven by a chain from the sprocket on the front of the crankshaft. The tension on the oil pump drive chain is accomplished by an adjustable guide.

### Oil Pan

The oil pan is constructed of stamped steel and is mounted to the lower crankcase. The oil pan includes a baffle that helps prevent the oil from shifting away from the oil pump suction pipe during hard turns, acceleration or stopping.

### Cylinder Head

The cylinder head is an aluminum alloy casting with pressed-in valve guides and valve seat inserts. The fuel injection nozzles are located in the intake ports.

The cylinder head has four in-line combustion chambers. Each combustion chamber has two intake valves and two exhaust valves.

A fuel injector is positioned near each set of intake valves. During each intake stroke of the engine, a fuel injector sprays or atomizes fuel into a fine mist. This mist mixes with air drawn in through the intake manifold as the piston reaches the bottom of the cylinder during the intake stroke.

### Valves

The valve train is driven by a double overhead camshaft. Each camshaft has eight cam lobes. Each cam lobe operates an intake or exhaust valve. Valve lash is not adjustable. Valve Lash is provided for by Hydraulic Valve Lash (HVL) Adjusters.

There are two intake and two exhaust valves per cylinder. There are two valve springs per valve. The valve springs are conical-shaped to fit inside the valve lifter body. Positive valve stem seals are used on all valves.

### Valve Lifters

Direct acting hydraulic valve lifters are used. The valve lifter body includes a hardened iron contact foot bonded to a steel shell. These lifters are not repairable.

### Valve Lifter (Hydraulic Valve Lash Adjuster) Operation

The Hydraulic Valve Lash (HVL) Adjuster located between the camshaft and the valve stem is a direct acting type.

With the engine oil delivered into it from the oil pump, the HVL adjuster operates as follows to adjust the valve lash (clearance) to 0 automatically at all times.

1. When the camshaft is not depressing the HVL adjuster, the adjuster is held against the camshaft and the valve stem by the plunger spring. In this state, the valve lash is kept at 0. (At 0 valve lash, the oil pressure becomes equal in the A (1) and B (2) chambers, and the check ball closes the passage between these two chambers.
2. When the lobe of the camshaft starts pressing the HVL adjuster, the adjuster and plunger are pushed downward at the same time the body is pushed upward by the counterforce from the valve stem. As a result, the B (2) chamber is compressed and the pressure rises inside the HVL adjuster. The engine oil in the B (2) chamber will leak through the slight clearance between the body and the plunger. However, since the compression time is very short, the volume of engine oil in the B (2) chamber will only change slightly and the HVL adjuster (plunger and body as one unit) push down the valve stem to open the valve.
3. When the pushing of the camshaft against the HVL adjuster is over, the operation starts again as described in step 1. As the oil pressure in the B (2) chamber is lower than that in A (1) (the oil in the B (2) chamber under high pressure has leaked gradually -- refer to step 2), the oil pressure in the A (1) chamber pushes the check ball open to allow the engine oil to flow from the A (1) chamber to the B (2) chamber until the oil pressure becomes equal between the two chambers.

### Camshaft

Two camshafts are used, one for all intake valves, the other for all exhaust valves. The camshafts are cast iron. The exhaust camshaft rear end is slotted to mate with, and drive the camshaft position sensor.

### Camshaft Housings and Caps

The camshaft housings and caps are cast aluminum. The camshafts run directly on the housings and caps without bearing inserts.

### Camshaft Drive

Two roller timing chains are used. One chain is driven from the crankshaft and drives an idler gear. A second chain is driven from the idler gear and drives the camshafts.

A mechanical, ratcheting tensioner applies tension to an adjustable guide on the slack side of the crankshaft timing chain. A fixed guide controls crankshaft chain motion on the tension side of the chain.

An hydraulic tensioner and an upper guide control camshaft chain motion. The hydraulic tensioner incorporates a guide which applies tension to the slack side of the camshaft timing chain.

### Timing Chain Housing and Cover

The timing chain housing is die cast aluminum and retains the crankshaft front seal.

### Cylinder Head Cover

The cylinder head cover is die cast aluminum and houses the ignition coils.

### Intake and Exhaust Manifold

The intake manifold is made of aluminum. The exhaust manifold is cast iron.