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Question on Thermal Wax Valves - Two different ones?
Hey guys,
Quick question, can someone clarify what the purpose of these two valves are? Is one of these responsible for the cold start high idle? Or is that the sensor on the radiator....I have an 87 NA S4. And i see both these valves on my intake manifold.
Last edited by maaaaackle; Jan 10, 2026 at 05:02 PM.
The plastic thermowax valve with the two vacuum nipples is used to keep your secondary throttle plates closed until the throttle body is at operating temperature so the air temp sensor at the throttle body can give correct readings. The second, all metal one is what actuates the cold idle cam by pushing on an adjustable cam to wedge out the primary throttle slightly to raise idle. Once warm, it pushes the cam completely out of the way of the primary throttle, allowing the throttle to close completely
