For 1990-2009 cars

### Testing Procedure

A compression pressure test of the engine cylinders determines the condition of the rings, the valves and the head gasket.

1. Run the engine until it reaches normal operating temperature. The battery must be at or near full charge.
2. Turn the engine OFF.
3. Disable the ignition.
4. Disable the fuel systems.

Important: Remove the Powertrain Control Module (PCM) and the ignition fuses from the I/P fuse block. Refer to Engine Electrical.

5. Remove the spark plugs from all cylinders.
6. Remove the air duct from the throttle body.
7. Block the throttle plate in open position.
8. Measure the engine compression, using the following procedure:

8.1. | Install the compression gauge firmly to the spark plug hole.

8.2. | Have an assistant crank the engine through, at least four compression strokes, in the testing cylinder.

8.3. | Check and record the readings on the gauge at each stroke.

8.4. | Disconnect the gauge.

8.5. | Repeat the compression test for each cylinder.

9. Record the compression readings from all of the cylinders.

• | The lowest reading should not be less than 70% of the highest reading.

• | No cylinder reading should be less than 689 kPa (100 psi).

10. The following are examples of measurement problems:

• | When the compression measurement is normal, the compression builds up quickly and evenly to specified compression on each cylinder

• | When the piston ring compression is low on the first stroke and tends to build up on the following strokes, but does not reach normal. Compression improves considerably with the addition of oil. Use approximately three squirts of oil from a plunger-type oiler.

• | When the leaking head gaskets give nearly the same results as valve problems, but may be identified by engine coolant in the crankcase. head gasket leakage between two cylinders will give low readings on both cylinders.

11. Remove the block from the throttle plate.
12. Install the air duct to the throttle body.
13. Install the spark plugs.
14. Install the Powertrain Control Module (PCM) fuse.
15. Install the ignition fuse to the I/P fuse block.