Compression Check: Testing and Inspection

COMPRESSION
If the engine exhibits low power, poor fuel economy, or poor idle, check the following:
1. Ignition system.
2. Compression.
3. Fuel system.

INSPECTION
1. Verify that the battery is fully charged. Recharge it if necessary.
2. Warm up the engine to the normal operating temperature.
3. Stop the engine and allow it to cool for about 10 minutes.
4. Remove the spark plugs on the exhaust side only.





5. Disconnect the harness connectors from the ignition coils.
6. Connect a compression gauge to No.1 spark plug hole.
7. Fully depress the accelerator pedal and crank the engine.
8. Note the maximum gauge reading.
9. Check each cylinder as above.





COMPRESSION PRESSURE LIMIT CHART
The compression pressures are considered within specification if the lowest reading cylinder is within 75% of the highest.
Compression:
Lowest reading cylinder within 75 percent of the highest. (Refer to image.)

10. If the compression in one or more cylinders is low, pour a small amount of engine oil into the cylinder and recheck the compression.
(1) If the compression increases, the piston, piston rings, or cylinder wall may be worn.
(2) If the compression stays low, the valve may be stuck or seating improperly.
(3) If the compression in adjacent cylinders stays low, the cylinder head gasket may be damaged or the cylinder head distorted.

11. Connect the harness connectors to the ignition coils.
12. Install the spark plugs.
Tightening torque:
7-14 Nm (0.7-1.4 kgf.m, 5-10 ft.lbf)