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.
Engine Compression
Check engine compression with engine at normal operating temperature at specified cranking speed, all spark plugs removed (on dual plugs, remove exhaust side only) and throttle wide open. Ensure crankcase is full and oil is correct viscosity. With compression gauge installed, use remote starter to crank engine.
Crank engine at least 5 revolutions and record highest reading. Repeat procedure for all cylinders using approximately the same number of revolutions. The lowest compression reading should not be less than 75 percent of the highest compression reading. No cylinder compression reading should be less than 100 psi (7 kg/cm2 ).
| Application | Compression Ratio | ||
|---|---|---|---|
| 4.6L | 9.0:1 | ||
| 5.0L | 8.9:1 | ||
| 5.0L MA (1) | 9.0:1 | ||
| 5.8L | 8.3:1 | ||
|
|||
NO RELATED
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Affiliate disclosure: We may earn a commission at no extra cost to you.
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.