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 MANUALSPONTIAC1991SUNBIRD BASE, 4D SEDAN, STANDARDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - BASIC TESTINGNO START DIAGNOSIS (A3)NO START - ENGINE CRANKS OKAY (TBI WITH DIS)IGNITION SYSTEM
1991 Pontiac Sunbird Base, 4D Sedan, Standard
Ignition System
1991 Pontiac Sunbird Base, 4D Sedan, StandardSECTION Ignition System
- Disconnect tachometer wire (if equipped). A shorted tachometer or tachometer circuit will not allow vehicle to start.
- With ignition on, check for battery voltage at Pink or Pink/Black wire of 2-wire connector at ignition module. Check for continuity to ground on Black/White wire of 2-wire connector. Repair as necessary.
- Connect ST-125 spark tester to end of one plug wire and crank engine. Leave matching plug wire connected to spark plug. If spark occurs, check spark on matching wire. If spark occurs on both wires, check fuel system. If spark occurs on only one wire, proceed to step 5).
- If spark does not occur on both wires, remove crankshaft sensor and check resistance. On 2.5L engine, it is necessary to remove ignition module in order to remove sensor. Resistance should be 800-900 ohms at room temperature. Lay a flat piece of metal on tip of sensor to determine if sensor is still magnetized. Replace if necessary. If sensor is okay, check wiring harness to and from ignition module for opens or shorts. If harness is okay, replace ignition module.
- If spark occurred on only one wire in step 3), note which wire had no spark. Turn ignition off and remove ignition coils. Check for carbon tracking or faulty connections between coil and ignition module. Repair or replace as necessary. If no problems are noticeable, switch coil positions on module and recheck for spark.
- If same plug wire has no spark, replace ignition module. If spark now occurs on plug wire which previously had no spark and no spark occurs on a different plug wire, replace defective ignition coil.
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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.