This procedure tests the compression pressure in each cylinder of the 1.5L turbocharged engine to diagnose internal engine condition, valve sealing, and piston ring wear.

Warnings

Tools required

Parts

• Spark plugs (if fouled or damaged) × 4 — NGK DILKAR8A8 or equivalent OEM

Preparation

1. Ensure engine is at normal operating temperature (coolant temperature above 80°C/176°F)
2. Park vehicle on level surface and engage parking brake
3. Allow engine to cool for 10-15 minutes to reduce burn risk while remaining warm
4. Verify battery is fully charged (12.4V or higher at rest)
5. Gather all tools and have compression gauge ready with correct adapter

Procedure

1. 1

   Remove engine cover
   Locate and remove the plastic engine cover by pulling upward firmly on the front edge, then lifting away from the rear mounting grommets. Set aside in a clean area.
2. 2

   Remove ignition coils
   Disconnect the electrical connector from each ignition coil by pressing the release tab and pulling straight up. Remove the single 10mm bolt securing each coil. Pull each coil straight up with a slight twisting motion to remove from the spark plug well. Keep coils in order (cylinders 1-4 from timing belt side to transmission side).
3. 3

   Remove all spark plugs
   Use compressed air or a clean cloth to remove any debris from around the spark plug wells to prevent contamination. Using a 16mm spark plug socket with extension, carefully remove all four spark plugs. Inspect plugs for fouling, abnormal wear, or damage. Keep plugs in order for diagnosis.
   ⚠Spark plug wells can accumulate oil or debris. Clean thoroughly before removal to prevent contamination entering cylinders.
4. 4

   Disable fuel injection system
   Open the underhood fuse/relay box located on the driver's side of the engine bay. Locate and remove the PGM-FI MAIN relay (Relay 1 in the fuse box, typically a black 30A relay). This prevents fuel injection during compression testing and avoids cylinder flooding.
   ℹ️Refer to the fuse box diagram on the underside of the lid to confirm correct relay location.
5. 5

   Test cylinder 1 compression
   Install the compression gauge firmly into cylinder 1 spark plug hole (closest to timing belt/chain side). Ensure gauge is seated properly. Have an assistant fully depress the accelerator pedal to wide-open throttle and crank the engine for 5-6 compression strokes (approximately 3-4 seconds). Record the maximum pressure reading. Release gauge pressure valve.
   ⚠Throttle must be held wide open during all compression tests to ensure unrestricted airflow.
6. 6

   Test cylinder 2 compression
   Move compression gauge to cylinder 2. Repeat cranking procedure with throttle wide open for 5-6 compression strokes. Record maximum pressure reading. Release gauge pressure.
7. 7

   Test cylinder 3 compression
   Move compression gauge to cylinder 3. Repeat cranking procedure with throttle wide open for 5-6 compression strokes. Record maximum pressure reading. Release gauge pressure.
8. 8

   Test cylinder 4 compression
   Move compression gauge to cylinder 4 (closest to transmission side). Repeat cranking procedure with throttle wide open for 5-6 compression strokes. Record maximum pressure reading. Release gauge pressure.
9. 9

   Analyze compression results
   Compare all four readings. Standard compression pressure should be 1700-2000 kPa (247-290 psi) at cranking speed for this engine. Maximum variation between cylinders should not exceed 150 kPa (22 psi). Any cylinder reading below 1400 kPa (203 psi) or variation exceeding specification indicates potential valve, piston ring, or head gasket issues requiring further diagnosis.
   ℹ️If compression is low in adjacent cylinders, suspect head gasket failure. Low compression in all cylinders may indicate timing chain issues or excessive piston ring wear.
10. 10

    Reinstall spark plugs
    Inspect spark plug threads and electrodes. Apply a small amount of anti-seize compound to plug threads (avoid getting on electrode). Hand-thread each spark plug carefully to avoid cross-threading. Tighten spark plugs to 18 Nm (13 lb-ft). If plugs are worn or fouled, install new plugs to same specification.
    ⚠Do not over-torque spark plugs in aluminum head. Cross-threading will cause expensive head damage.
11. 11

    Reinstall ignition coils
    Apply a thin coat of dielectric grease to the inside of each coil boot. Install each coil into its correct cylinder, pushing down firmly until seated. Install the 10mm mounting bolt for each coil and tighten to specification. Reconnect each electrical connector until it clicks.
    Torque spec

    Sensor Bolts10 Nm (8 lb-ft)
12. 12

    Restore fuel system and test
    Reinstall the PGM-FI MAIN relay into the fuse/relay box. Close the fuse box cover. Turn ignition to ON position (without starting) for 2 seconds, then OFF, then ON again to prime fuel system. Start engine and verify smooth operation with no misfires.

Reassembly

1. Reinstall engine cover by aligning rear grommets first, then pressing down firmly on front clips until seated
2. Clear any diagnostic trouble codes that may have been set during testing using an OBD-II scanner
3. Verify no tools or parts are left in engine bay

Verification

• Start engine and verify smooth idle with no misfires or rough running
• Check for any oil leaks around spark plug wells after running engine for 2-3 minutes
• Confirm all ignition coil connectors are fully seated and secured
• Verify compression readings are within specification and variance between cylinders is acceptable
• Document all compression readings for future reference and trend analysis

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