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.
1985 Porsche 928 AutomaticFACTORY OEM SERVICE PROCEDURE
Air Regulating Valve
NOTE:
There is no simple way to test the idle positioner (air regulating valve).
- With engine at idle speed (690 RPM), screw in throttle by-pass screw completely when engine in running at steady idle speed. After brief deviation the idle speed must return to 690 RPM.
- Connect center connection of air regulator with a 12-volt power supply. Connect outer connection with ground. Air regulator must turn against stop. Exchange outer connections. Air regulator must turn to other stop.
- Connect a new regulating valve on the wire plug to check activation of air regulator from the control unit. Air regulator must vibrate noticeably (frequency activation) with engine running. If engine speed is boosted with the by-pass screw, the air regulator must move in closing direction. Air regulating valve must turn in opening direction when engine speed drops. If not, replace air regulating valve.
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.