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.
1987 Merkur XR4Ti AutomaticFACTORY OEM SERVICE PROCEDURE
Idle Speed Controller (ISC) Valve
- Check wiring and controller for damage or deterioration. Repair as necessary. Connect test light to idle speed actuator between Red wire and ground. Turn ignition on. If light is on, go to next step. If light is off, repair open in power feed circuit.
- Connect jumper wire from actuator Gray wire to ground and turn ignition on. If speed controller operates, go to next step. If not, replace idle speed controller.
- Using an ohmmeter check for continuity between wire at ECA pin No. 21 and Gray wire at controller. If no continuity, repair wiring. If continuity present, idle speed controller circuit is okay.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.