KIA Niro: Compression Pressure Inspection

Warning

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

1. Warm up and stop the engine.

   Allow the engine to warm up to normal operating temperature.

2. Remove the air cleaner.

   (Refer to Intake and Exhaust System - "Air Cleaner")

3. Remove spark plugs.

   (Refer to Engine Electrical System - "Spark Plug")

4. Check cylinder compression pressure.

(1) Insert a compression gauge into the spark plug hole. If possible, place the gauge where it can be seen from inside the vehicle.

(2) Attach the KDS.

• Connect the cable of KDS to the data link connector.
• Select the vehicle model and then the HCU system.
• Select the "Engine Test On". See the screens below.

(3) While cranking the engine, measure the compression pressure.

• With the Brake pedal depressed, press the Start/Stop Button (SSB) one time.
• If the engine cranks, let it crank about 8 to 10 cycles (until the gauge readings stabilizes) then press the SSB one time to stop the engine from cranking.
• If the engine does not crank on its own when the SSB is pressed, the KDS should be used to crank the engine. While in the "Engine Test On" follow the instruction on the screen.
• The "Engine Test On" will start the engine cranking. After the compression readings stabilize (8-10 cycles), press the SSB one time to stop the cranking.

(4) Repeat steps (1) through (3) for each cylinder.

Warning

Be sure ignition is in the OFF mode between each cylinder test.

This measurement must be done while the engine is still near operating temperature.

Compression pressure : 981kPa (10.0kgf/cm², 142psi) / 300 - 350rpm Minimum pressure :
834kPa (8.5kgf/cm², 121psi) / 300 - 350rpm Difference between each cylinder : 100kPa (1.0kgf/cm², 15psi) 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 steps (1) through (3) for cylinders with low compression.

• If adding oil helps the compression, it is likely that the piston rings and/or cylinder bore are worn or damaged.
• If pressure stays low, a valve may be sticking or seating is improper, or there may be leakage past the gasket.

5. Reinstall spark plugs.

Tightening torque : 14.7 - 24.5 N*m (1.5 - 2.5 kgf*m, 10.8 - 18.1 lb*ft)

6. Install ignition coils.

Tightening torque : 9.8 - 11.8 N*m (1.0 - 1.2 kgf*m, 7.2 - 8.7 lb*ft)

7. Connect the injector connectors and ignition coil connectors.
8. Some DTC's may exist after the inspection test and may need to be manually cleared with KDS.

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