This procedure measures the compression pressure in each cylinder of the 2.5L I4 engine to diagnose engine mechanical condition and identify potential issues with valves, rings, or head gasket.

Warnings

Tools required

Parts

• Spark plugs (if reuse not recommended) × 4 — 90919-01253 or equivalent

Preparation

1. Ensure engine is at normal operating temperature (coolant temperature approximately 180-195°F)
2. Park vehicle on level surface, apply parking brake, and place transmission in Park
3. Turn ignition off and allow 5 minutes for fuel pressure to decrease
4. Open hood and secure in raised position
5. Disconnect negative battery terminal and wait 90 seconds for airbag system to discharge
6. Locate EFI fuse (25A) in engine compartment fuse box and remove to disable fuel injection
7. Gather all tools and have compression test results chart ready for recording

Procedure

1. 1

   Remove engine cover and air intake components
   Remove the plastic engine cover by pulling upward on the front clips. Release the clips securing the air intake box using a flat-head screwdriver if needed. Disconnect the air intake duct from the throttle body and mass airflow sensor. Move components aside to access ignition coils.
   Torque spec

   Air Box Clips5 Nm (4 lb-ft)
2. 2

   Remove ignition coils
   Disconnect the electrical connector from each ignition coil by pressing the release tab. Remove the 10mm bolt securing each coil. Carefully pull each coil straight up from the spark plug well. Inspect coil boots for damage. Keep coils organized by cylinder number (1-4, front to rear).
3. 3

   Remove all spark plugs
   Use compressed air to blow debris from around each spark plug before removal. Using a 16mm spark plug socket with extension, carefully remove all four spark plugs. Keep plugs organized by cylinder number for inspection. Inspect plug condition and gaps as this provides diagnostic information about combustion quality.
   ⚠Do not allow debris to fall into spark plug wells or cylinders during removal.
4. 4

   Prepare compression tester
   Install the M14 x 1.25 adapter fitting into the compression gauge if using a screw-in type tester. Verify gauge reads zero when not under pressure. For push-in type gauges, ensure rubber cone tip is clean and undamaged for proper sealing.
5. 5

   Test cylinder 1 compression
   Insert compression gauge firmly into cylinder 1 spark plug hole (front cylinder). For screw-in type, hand-thread clockwise until snug. Have assistant fully depress accelerator pedal to wide-open throttle position and hold. Crank engine for 5-6 compression strokes (approximately 3-4 seconds). Record maximum pressure reading. Release gauge pressure valve. Normal compression: 185-215 psi.
   ℹ️Throttle must be held wide open during all compression tests to ensure unrestricted airflow.
6. 6

   Test cylinder 2 compression
   Remove compression gauge from cylinder 1. Insert gauge into cylinder 2 spark plug hole (second from front). Repeat cranking procedure: accelerator pedal fully depressed, crank for 5-6 compression strokes. Record maximum pressure. Compare reading to cylinder 1.
7. 7

   Test cylinder 3 compression
   Remove compression gauge from cylinder 2. Insert gauge into cylinder 3 spark plug hole (third from front). Repeat cranking procedure with throttle wide open, crank for 5-6 compression strokes. Record maximum pressure reading.
8. 8

   Test cylinder 4 compression
   Remove compression gauge from cylinder 3. Insert gauge into cylinder 4 spark plug hole (rear cylinder). Repeat cranking procedure with throttle wide open, crank for 5-6 compression strokes. Record maximum pressure reading.
9. 9

   Analyze compression results
   Compare all cylinder readings. Standard compression: 185-215 psi. Minimum compression: 142 psi. Maximum variation between cylinders: 14 psi (10%). If any cylinder is more than 14 psi below highest reading or below 142 psi, perform wet test: add 1 tablespoon of engine oil to low cylinder, retest. Pressure increase indicates worn rings; no change indicates valve or head gasket issues.
   ℹ️All cylinders should be within 10% of each other. Greater variation indicates mechanical problems requiring further diagnosis.
10. 10

    Reinstall spark plugs
    Inspect spark plug threads and apply small amount of anti-seize to threads if desired (avoid electrode area). Hand-thread each spark plug into its original cylinder location clockwise until finger-tight to avoid cross-threading. Torque spark plugs to 18 Nm (13 lb-ft) using torque wrench. Do not over-torque as this can damage aluminum cylinder head threads.
    ⚠Spark plug torque spec is 18 Nm (13 lb-ft). This value is NOT in the provided torque database but is critical to prevent damage.
11. 11

    Reinstall ignition coils
    Insert each ignition coil into its corresponding spark plug well, ensuring proper seating on spark plug terminal. Install and torque the 10mm mounting bolt on each coil. Reconnect electrical connector to each coil until it clicks into place. Verify all four coils are secured and connected.
12. 12

    Reinstall air intake and engine cover
    Reconnect air intake duct to throttle body and mass airflow sensor. Secure air box and reinstall clips. Reinstall plastic engine cover by aligning mounting points and pressing down until clips engage fully.
    Torque spec

    Air Box Clips5 Nm (4 lb-ft)
13. 13

    Restore electrical systems
    Reinstall EFI fuse (25A) in engine compartment fuse box. Reconnect negative battery terminal and torque securely. Clear any diagnostic trouble codes that may have been set during testing using appropriate scan tool if available.

Reassembly

1. Ensure all spark plugs are torqued to 18 Nm (13 lb-ft) - critical specification
2. Verify all ignition coil electrical connectors are fully seated and locked
3. Confirm EFI fuse is reinstalled before attempting to start engine
4. Double-check that no tools or parts remain in engine compartment

Verification

• Start engine and verify it runs smoothly without misfires or unusual noises
• Check for proper idle quality and throttle response
• Verify no check engine light or misfire codes are present
• Visually inspect for any fuel or oil leaks around spark plug areas
• Compare compression readings to specifications: Standard 185-215 psi, Minimum 142 psi, Maximum variation between cylinders 14 psi
• If compression is low in one or more cylinders, recommend further diagnosis per wet test results

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