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 Plymouth Colt BaseFACTORY OEM SERVICE PROCEDURE
Throttle Position Sensor/Switch: CARBURETED
- Loosen accelerator cable tension. Loosen idle speed adjusting screws to completely close throttle valve (count and record number of turns out). Ensure fast idle cam is not holding throttle valve open. Disconnect carburetor wire connectors and install Test Harness (MD998464). Connect DVOM to terminal No. 8 (Blue Clip on harness) and terminal No. 3 (Red clip) of the harness.
- Turn ignition switch to "ON" position. DVOM should read .25 volt. If outside this range loosen TPS and turn until correct reading is obtained (clockwise increases voltage). Tighten TPS. Turn ignition to "OFF" position. Remove test harness.
- Reset idle speed screws as recorded in step 1). Start engine. Check idle speed. Idle should be 625-900 rpm.
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.