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.
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HOMESERVICE MANUALSPONTIAC1988FIREBIRD BASE, 5.0 E, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCETESTING & DIAGNOSIS1987-88 COMPUTERIZED ENGINE CONTROLSCHART C1D - MAP OUTPUT CHECK
1988 Pontiac Firebird Base, 5.0 E, Standard
Chart C1D - Map Output Check
1988 Pontiac Firebird Base, 5.0 E, StandardSECTION Chart C1D - Map Output Check
The MAP measures manifold pressure (vacuum) and sends that signal to ECM. ECM uses this information for fuel and spark control.
- Checks MAP sensor output voltage to ECM. This voltage, without engine running, represents a barometer reading to ECM.
- Applying 10 in. Hg (34 kPa) vacuum to MAP sensor should cause voltage to be 1.2 volts less than voltage at step 1). Upon applying vacuum to sensor, change in voltage should be instantaneous. A slow voltage change indicates a faulty sensor.
- Check vacuum hose to sensor for leaking or restriction. Be sure no other vacuum devices are connected to MAP hose.
IGNITION ON, ENGINE OFF VOLTAGES (LOW ALTITUDE = HIGH PRESSURE = HIGH VOLTAGE)
| ALTITUDE Meters | ALTITUDE Feet | VOLTAGE RANGE |
|---|---|---|
| Below 305 | Below 1,000 | 3.8-5.5V |
| 305-610 | 1,000-2,000 | 3.6-5.3V |
| 610-914 | 2,000-3,000 | 3.5-5.1V |
| 914-1219 | 3,000-4,000 | 3.3-5.0V |
| 1219-1524 | 4,000-5,000 | 3.2-4.8V |
| 1524-1829 | 5,000-6,000 | 3.0-4.6V |
| 1829-2133 | 6,000-7,000 | 2.9-4.5V |
| 2133-2438 | 7,000-8,000 | 2.8-4.3V |
| 2438-2743 | 8,000-9,000 | 2.6-4.2V |
| 2743-3048 | 9,000-10,000 | 2.5-4.0V |
RENDER: 1.0x
NO RELATED
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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.