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. To check engine compression with a compression gauge, bring engine to normal operating temperature. Disconnect fuel injector connectors. Remove ignition coils. Remove all spark plugs. Fully open throttle. Ensure engine cranking speed is at least 250 RPM when measuring compression. Repeat engine compression test procedure at least 2 times.
| Application | Specification | |
|---|---|---|
| Compression Ratio | 10.5:1 | |
| Compression Pressure | ||
| ES300 | 218 psi (15.3 kg/cm2 ) | |
| GS300 & SC300 | 192 psi (13.5 kg/cm2 ) | |
| GS400, LS400 & SC400 | 178 psi (12.5 kg/cm2 ) | |
| Minimum Compression Pressure | ||
| ES300 | 145 psi (10.2 kg/cm2 ) | |
| GS300 & SC300 | 156 psi (11.0 kg/cm2 ) | |
| GS400, LS400 & SC400 | 142 psi (10.0 kg/cm2 ) | |
| Maximum Variation Between Cylinders | 14 psi (1.0 kg/cm2 ) | |
Use the Manual With the Right Hardware
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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.
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