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 PERFORMANCETUNE-UPIGNITION SYSTEM - DIRECTTESTINGEST PERFORMANCE CHECK
1988 Pontiac Firebird Base, 5.0 E, Standard
Est Performance Check
1988 Pontiac Firebird Base, 5.0 E, StandardSECTION Est Performance Check
- The ECM will set timing at a specified value when diagnostic test terminal of the ALDL connector is grounded. To check the EST operation, perform the following steps:
- Start and run engine at 1500 RPM with the ALDL diagnostic test terminal NOT grounded. Ground test terminal. When ALDL test terminal is grounded there should be a noticeable change in engine RPM. When a fault in the EST system takes place, a code 42 should be set.
- If code 42 is set, use appropriate chart for diagnosis. If symptom is engine miss and the direct ignition system is suspect, use CHART C-4D DIS MISFIRE in the 2.8L VINS [S,9] PFI CEC TESTS W/CODES article in the ENGINE PERFORMANCE section for proper diagnosis.
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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.