2. Operate the vehicle while the engine is at normal operating temperature.
3. Disconnect the spark plug wires from the spark plug.
4. Disconnect the fuel injector electrical connector.
5. Remove all spark plugs.
Note: Do not insert foreign objects into the throttle bore. Damage to the electronic throttle body may require replacement of the entire electronic throttle body assembly.
6. Lock the throttle lever in its wide open position.
7. Install the engine cylinder compression gauge on the cylinder being tested.
8. Using the vehicle's starter, crank or turn the engine crankshaft through 4 compression or exhaust strokes for the cylinder being tested. If the engine cranks more than 4 compression strokes, retest the cylinder.
9. Record the compression values.
10. Remove the compression gauge from the engine cylinder being tested.
11. Repeat steps 8–11 for each additional cylinder. To obtain reliable test results, all cylinders on the engine must be tested.
12. If any of the cylinders have low compression, inject approximately 15 ml of engine oil into the cylinder through the spark plug hole.
13. Repeat steps 8-11 for all low compression cylinders.
14. The minimum compression ratio in any cylinder must be at least 70 percent of the cylinder with the highest compression ratio. No cylinder should have a pressure less than 690 kPa (100 psi). For example, if the highest pressure in any cylinder is 1035 kPa (150 psi), then the lowest allowable pressure for any other cylinder must be 725 kPa (105 psi). Multiply the highest pressure in the cylinder by 70%: 1035 kPa x 70% = 725 kPa (150 psi x 70% = 105 psi). This must be done to determine the lowest allowable pressure in any other cylinder.
- Normal: Compression increases quickly and evenly to a precisely defined compression level.
- Piston ring leakage: Compression is low on the first compression stroke. Compression increases on subsequent compression strokes but does not reach normal values. Compression improves significantly after adding oil.
- Valve leakage: Compression is low on the first compression stroke. Compression does not increase on subsequent compression strokes and does not reach normal values. Compression does not improve significantly or at all after adding oil.
- Cylinder Head Gasket Leak: Compression is low on the first compression stroke. Compression does not increase on subsequent compression strokes and does not reach normal values. Compression does not improve significantly or at all after adding oil. Adjacent cylinders have the same or similar low compression readings.
15. If the compression in one or more cylinders reaches the minimum predetermined compression value, all damaged or worn components must be repaired or replaced and the engine retested.