While checking the various Wires/Terminals around the Engine Bay yesterday, I disconnected a single Wire Black Plastic Terminal that is located at the top of the Engine, over the Intake Manifold, near the Engine front. The Engine was running (I was trying to track down the cold start stumbles), and when I pulled the two halves apart, I heard a distinct Metallic Clunk toward the front of the Engine, near the Water Pump. Not to be timid with disconnecting things when the Engine was running, I reconnected it and disconnected it again, getting the same Metallic Clunk. No change in the Engine note, just the Clunk. It doesn't appear to be under the Valve Cover but toward the front/top of the Engine.
Any idea on what this is? Sounds like a Valve opening and closing.
Sam ('86 190e 2.3)