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.
1989 Geo Prizm Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Idle Speed: Notes
- Ensure air cleaner and all electrical connections and emission hoses are properly installed. Warm engine to normal operating temperature. Turn engine off. Ensure all accessories are off.
- Remove cover from diagnostic cover, located on left strut tower. Connect tachometer to specified terminal of diagnostic connector and to the battery. See Figure
.CAUTION: DO NOT ground tachometer terminal in diagnostic connector, as grounding terminal could result in ignitor or ignition coil damage.
- Install jumper wire between terminals E1 and "T" or TE1 of diagnostic connector. See Figure . Start engine and note idle speed. Idle speed should be within specification. See IDLE SPEED SPECIFICATIONS table.
- If idle speed requires adjustment, remove plug and rotate idle speed adjusting screw to obtain correct idle speed. See Fig 1 and Fig 2 .
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.