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 Ford Mustang LX, 2D Hatchback, 5.0 E, AutomaticFACTORY OEM SERVICE PROCEDURE
Extended Idle Air By-Pass System
- With engine at normal operating temperature and transmission in "N", begin timing. If after 2 1/2 minutes Thermactor By-Pass Valve releases secondary air through vents, system is operating properly. If not, check routing and condition of hoses, and of By-Pass Valve.
- If valve is operating correctly, check battery voltage to ITS. Also check for continuity through normally closed ITS while manually cycling switch. If correct, check that solenoid is functional and actually opens to close off vacuum. If solenoid is okay, turn engine off. Turn ignition switch to "ON" position. After 2 1/2 minutes, check vacuum signal to solenoid.
Factory Service Tools
Use the Manual With the Right Hardware
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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.
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