This procedure tests the compression of each cylinder in the 1.5L turbocharged engine to diagnose internal engine condition and identify worn rings, valves, or head gasket issues.

Warnings

Tools required

Parts

• Spark plug set (if reusing old plugs is not advisable) × 4 — NGK DILKAR8H8S or OEM equivalent

Preparation

1. Ensure engine is completely cold (not run for at least 2 hours)
2. Park vehicle on level surface and engage parking brake
3. Open hood and disconnect negative battery terminal to prevent starter damage during testing
4. Relieve any residual fuel pressure by removing fuel pump fuse and attempting to start (engine will not start with battery disconnected)
5. Locate all four spark plugs on top of engine under ignition coil packs

Procedure

1. 1

   Remove engine cover
   Grasp the engine cover firmly and pull upward to disengage the mounting grommets. The cover is held by friction fit grommets and does not require tools. Set aside in a clean area.
2. 2

   Remove ignition coil connectors
   Disconnect the electrical connector from each of the four ignition coils by pressing the locking tab and pulling straight up. Label or photograph connector positions if needed for reassembly.
3. 3

   Remove ignition coils
   Remove the mounting bolt from each ignition coil using a 10mm socket. Pull each coil straight up with a twisting motion to break the seal. Keep coils organized by cylinder position (1-4 from timing belt side to transmission side).
   Torque spec

   Sensor Bolts10 Nm (8 lb-ft)
4. 4

   Remove all spark plugs
   Using a 14mm or 16mm spark plug socket with extension, carefully remove all four spark plugs. Turn counterclockwise and ensure socket is fully seated to prevent rounding. Keep plugs in order by cylinder number for analysis. Inspect plugs for oil fouling, carbon buildup, or abnormal wear patterns.
5. 5

   Disable fuel injection system
   Locate the fuel injector connector(s) near the fuel rail and disconnect them to prevent fuel from entering cylinders during testing. This prevents raw fuel from washing cylinder walls and contaminating oil.
6. 6

   Prepare compression tester
   Install the appropriate M14 x 1.25 adapter into the compression tester. Ensure the tester gauge is zeroed or can be reset between cylinder tests. Verify all connections are secure to prevent pressure leaks.
7. 7

   Test cylinder 1 compression
   Thread the compression tester adapter hand-tight into cylinder 1 spark plug hole (closest to timing belt). Ensure tester is fully seated. Have helper fully depress accelerator pedal to open throttle plate, then crank engine for 5-6 compression strokes (approximately 5 seconds). Record the maximum pressure reading. Release pressure valve and remove tester.
8. 8

   Test remaining cylinders
   Repeat the compression test procedure for cylinders 2, 3, and 4 in order. For each cylinder: install tester hand-tight, open throttle fully, crank for 5-6 strokes, record maximum pressure, and release tester. Maintain consistent cranking duration for accurate comparison between cylinders.
9. 9

   Analyze compression results
   Compare all four cylinder readings. Normal compression should be 170-220 psi with no more than 10% variance between cylinders. Low compression in one cylinder indicates valve or piston ring issues in that cylinder. Low compression in adjacent cylinders suggests head gasket failure. Uniformly low compression across all cylinders indicates worn piston rings.
10. 10

    Perform wet test if needed
    If any cylinder shows low compression, add approximately 1 tablespoon of clean engine oil through the spark plug hole into that cylinder. Reinstall compression tester and retest. If compression increases significantly (30+ psi), piston rings are worn. If compression remains the same, valves or head gasket are likely the issue.
11. 11

    Reinstall spark plugs
    Inspect spark plug threads and apply a small amount of anti-seize to threads if desired (avoid getting anti-seize on electrodes). Thread each spark plug by hand into its original cylinder position to prevent cross-threading. Tighten spark plugs to specification using torque wrench. New plugs should be torqued to 20 Nm (15 lb-ft); reused plugs should be torqued to 18 Nm (13 lb-ft).
12. 12

    Reinstall ignition coils
    Apply dielectric grease to the inside of each coil boot. Press each ignition coil firmly into its corresponding spark plug until fully seated. Install mounting bolts and torque to specification.
    Torque spec

    Sensor Bolts10 Nm (8 lb-ft)
13. 13

    Reconnect electrical connections
    Reconnect all ignition coil electrical connectors, ensuring they click into place. Reconnect fuel injector connector(s). Reinstall engine cover by aligning grommets and pressing down firmly until seated.
14. 14

    Reconnect battery and initialize
    Reconnect negative battery terminal. Turn ignition to ON position (do not start) for 30 seconds to allow fuel system to prime. If power windows were operated during testing, perform window initialization by fully lowering then fully raising each window and holding the switch up for 2 seconds.

Reassembly

1. Ensure all ignition coil connectors are fully seated and locked
2. Verify engine cover grommets are properly engaged
3. Double-check that no tools or parts were left in engine bay

Verification

• Start engine and verify it runs smoothly without misfires
• Check for any unusual noises or rough idle that may indicate incorrect spark plug installation
• Verify no check engine light appears after starting
• Rev engine slightly to confirm all cylinders are firing properly
• Review compression test results: acceptable readings are 170-220 psi with less than 10% variance between cylinders

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