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There was a thread a while back about some of having an issue with the DSI clucking back to start position some time after the engine's been turned off. Thinking about it, doesn't that mean it also doesn't work properly at speed (5 or 6000 RPM)? If I understand this correctly, the DSI is in the short position (least restriction) when the car is off. When it's started, it stays in this position until it's running and then switches to the long path position until 5-6K sepending on your computer ROM version. Comments anyone?
 

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I believe the DSI rotates back and forth to help keep build up from making it stick in one position or the other.
 

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i think it's the opposite, it stays in the short position when the car is not on, but once the car turns on, it will automatically turn to the long runners, becasue that's where we get the low end grunt that we are suppose to have. when we shut the car off, you can hear this plastic clunk sound from time to time which means that it's returning to the short runners
 

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Here's another way to describe what's going on. The DSI "opens" at high RPM to shorten the intake path and "closes" at low RPM to make the intake runners longer. This is acheived using spring tension for opening and a cable actuator for closing.

At rest (shut off), the actuator releases tension which opens the runners. I've read that this was dsone to prevent the runners from sticking in the closed position. Many people hear the opening of the DSI as a clunk. I've never noticed it, but I've often reached in and rotated the DSI manually to check up on the health of the cable linkage (often referred to as the DSI Clip). When released, it does thump a bit (which is different than a clunk, probably due to the hood being open... :p)
 
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