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 MANUALSPONTIAC1987FIERO BASE, STANDARD, MG3REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCEADJUSTMENTTUNE-UP - V6ADJUSTMENTSIDLE SPEED CONTROL MOTOR3.8L (VIN A)
1987 Pontiac Fiero Base, Standard, MG3
3.8L (VIN A)
1987 Pontiac Fiero Base, Standard, MG3SECTION 3.8L (VIN A)
- Remove plunger. Measure and record length of plunger (distance "A"). See Fig 1 . Install plunger into ISC and position so that distance measured from back side of plunger to ISC is less than distance "B". See IDLE SPEED CONTROL PLUNGER SETTING chart.
- Place transmission in Neutral (man. trans.) or in "P" (auto. trans.). Set brakes and block wheels. Connect tachometer to engine. Connect dwell meter to mixture control solenoid (Green) lead. Set dwell meter on 6-cylinder scale. Turn A/C off (if equipped).IDLE SPEED CONTROL PLUNGER SETTING
Application Dimension "A" In. (mm) Dimension "B" In. (mm) 3.8L (VIN A) 41/64" (16.3) 5/16" (8.0) - Start engine. Run until engine enters "Closed Loop" operation (dwell meter needle starts to fluctuate). Stop engine.CAUTION: DO NOT disconnect or connect ISC connector with ignition in the "ON" position or damage to ECM may result.
- Unplug ISC connector from motor. Retract plunger by applying 12 volts to terminal "C" and grounding terminal "D" of ISC motor. See Fig 2 . DO NOT leave 12 volts connected to ISC motor any longer than necessary to retract plunger.
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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.