Compression Check
Measurement of Compression Pressure1. Warm up engine.
2. Turn ignition switch OFF.
3. Release fuel pressure. Refer to Powertrain Management; Fuel Delivery and Air Induction.
4. Remove all spark plugs.
^ Clean area around plug with compressed air before removing the spark plug.
5. Disconnect camshaft position sensor harness connector at the distributor.
6. Disconnect all fuel injector harness connectors.
7. Attach a compression tester to No. 1 cylinder.
8. Depress accelerator pedal fully to keep throttle valve wide open.
9. Crank engine and record highest gauge indication.
10. Repeat the measurement on each cylinder.
^ Always use a fully-charged battery to obtain specified engine speed.
Compression pressure:
Standard 1,226kPa (12.5kg/cm2, 178psi) /300 rpm
Minimum 1,030kPa (10.5kg/cm2, 149psi) /300rpm
Difference limit between cylinders 98kPa (1.0kg/cm2, 14psi) /300rpm
11. If compression in one or more cylinders is low:
a. Pour a small amount of engine oil into cylinders through spark plug holes.
b. Retest compression.
^ If adding oil helps compression, piston rings may be worn or damaged. If so, replace piston rings after checking piston.
^ If pressure stays low, a valve may be sticking or seating improperly. Inspect and repair valve and valve seat. If valve or valve seat is damaged excessively, replace.
^ If compression stays low in two cylinders that are next to each other:
a. The cylinder head gasket may be leaking, or
b. Both cylinders may have valve component damage. Inspect and repair as necessary.
12. Reconnect fuel pump fuse, all fuel injector harness connectors, and camshaft position sensor harness connector at the distributor and reinstall spark plugs.
13. Erase the DTC stored in the ECM.
CAUTION: Always erase the DTC after checking compression.