Compression Pressure Inspection

NOTE: If the there is lack of power, excessive oil consumption or poor fuel economy, measure the compression pressure.

Warm up engine until the normal operating temperature (80~95°C (176-203°F)).
Remove the surge tank. Refer to INTAKE AND EXHAUST SYSTEM .
Remove the ignition coil connectors (A) and ignition coils (B).

Fig 1: Ignition Coil Connectors
Courtesy of KIA MOTORS AMERICA, INC.

Fig 2: Ignition Coils
Courtesy of KIA MOTORS AMERICA, INC.
Remove the spark plugs.
Using a 16 mm plug wrench, remove the 6 spark plugs.
Check cylinder compression pressure.
1. Insert a compression gauge into the spark plug hole.
2. Fully open the throttle.
3. Crank the engine over 7 times to measure compression pressure.
  NOTE: Always use a fully charged battery to obtain engine speed of 250 RPM or more.
4. Repeat step 1 though 3 for each cylinder.
  NOTE: This measurement must be done in as short a time as possible.
  
  Compression pressure:
  
  1, 029 kPa (10.5kgf/cm² , 149 psi) (250~400 RPM)
  
  Minimum pressure:
  
  882 kPa (9.0kgf/cm² , 128 psi)
  
  Difference between each cylinder:
  
  98 kPa (1.0kg/cm² , 14 psi) or less
5. If the cylinder compression in 1 or more cylinders is low, pour a small amount of engine oil into the cylinder through the spark plug hole and repeat step 1 through 3 for cylinders with low compression.
  1. If adding oil helps the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged.
  2. If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.
Reinstall the spark plugs.
Install the ignition coils and ignition connectors.
Install the surge tank. Refer to INTAKE AND EXHAUST SYSTEM .