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
Warm engine to normal operating temperature before checking compression. Ensure battery is fully charged. Remove ignition coils and spark plugs. On all vehicles except GX470, see IGNITION SYSTEM in REMOVAL & INSTALLATION - EXCEPT GX470 article. On GX470, see IGNITION SYSTEM in REMOVAL & INSTALLATION - GX470. Check engine mechanical condition with a compression gauge, vacuum gauge, or engine analyzer with throttle fully open. See engine analyzer manual for specific instructions. See COMPRESSION SPECIFICATIONS table. Install and tighten spark plugs to 13 ft. lbs. (18 N.m).
| Application | Specification | |
|---|---|---|
| Normal Compression Pressure | ||
| ES300 & RX300 | 218 psi (15.3 kg/cm2 ) | |
| GS300, IS300 & LX470 | 192 psi (13.5 kg/cm2 ) | |
| GS430, GX470, LS430 & SC430 | 178 psi (12.5 kg/cm2 ) | |
| Minimum Compression Pressure | ||
| ES300 & RX300 | 145 psi (10.2 kg/cm2 ) | |
| GS300 & IS300 | 156 psi (11.0 kg/cm2 ) | |
| GS430, GX470, LS430, LX470 & SC430 | 142 psi (10.0 kg/cm2 ) | |
| Maximum Variation Between Cylinders | ||
| Except ES300 & RX300 | 14 psi (1.0 kg/cm2 ) | |
| ES300 & RX300 | 15 psi (1.1 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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