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.
SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSPONTIAC1991FIREBIRD BASE, 2D CONVERTIBLE, 3.1 T, 4L60/MD8REPAIR AND DIAGNOSISENGINE PERFORMANCESPECIFICATIONSENGINE CONTROLS - SPECIFICATIONS - V8MECHANICAL CHECKSENGINE COMPRESSION
1991 Pontiac Firebird Base, 2D Convertible, 3.1 T, 4L60/MD8
Engine Compression
1991 Pontiac Firebird Base, 2D Convertible, 3.1 T, 4L60/MD8SECTION Engine Compression
Check engine compression under the following conditions: engine at normal operating temperature and specified cranking speed, all spark plugs removed, and throttle wide open.
COMPRESSION SPECIFICATIONS
| Application | Specification | |||
|---|---|---|---|---|
| Compression Ratio | ||||
| 4.9L (VIN B) | 9.5:1 | |||
| 5.0L (VIN E & F) | 9.3:1 | |||
| 5.7L (VIN 7) | 9.8:1 | |||
| 5.7L (VIN 8) | 10.25:1 | |||
| Normal Compression Pressure | ||||
| 4.9L (VIN B) | 140-165 psi (10-12 kg/cm2 ) | |||
| All Others | (1) | |||
| Minimum Compression Pressure | (1) | |||
|
||||
RENDER: 1.0x
NO RELATED
Recommended Tools & Savings
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.