Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Mechanical Inspection: Compression
Check engine mechanical condition with a compression gauge, vacuum gauge, or an engine analyzer. See engine analyzer manual for specific instructions. Ensure battery is fully charged, engine is at normal operating temperature and throttle valve is fully open when checking the compression.
Remove Auto Shutdown (ASD) relay to prevent engine from starting when checking the compression. ASD relay is located behind driver's side strut tower at rear corner of engine compartment and contains a Gray 9-pin connector. See Fig 1 . Once compression test is complete, reinstall ASD relay and use scan tool to clear Diagnostic Trouble Code (DTC) from Powertrain Control Module (PCM). See appropriate TESTS W/CODES - NON-TURBO article for clearing of DTC.
| Application | psi (kPa) | |||
|---|---|---|---|---|
| 4-Cylinder | ||||
| Normal Compression Pressure | 170-225 (1172-1551) | |||
| Minimum Compression Pressure | 100 (689) | |||
| Maximum Variation Between Cylinders | (1) | |||
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.