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.
1990 Geo Tracker LSi, StandardFACTORY OEM SERVICE PROCEDURE
Idle Speed Control Solenoid Function Test
- Warm engine to normal operating temperature and monitor engine RPM. With engine idling, turn on headlights and blower fan. Idle speed should increase or maintain previous level. If idle speed does not increase or at least maintain previous level, check electrical load signals at Yellow connector terminal No. 3 of ECM.
- If electrical load signals are okay, check ISC solenoid. If solenoid is okay, check harness between ISC solenoid and control unit. If harness is okay, control unit is defective.
Factory Service Tools
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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.