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Hi everyone this is my first post to the MB forum, I bought a 2008 c300 recently and gave it to my girlfriend. It has 103k miles, and I got it for a very decent price due to a couple leaks and upcoming maintenance needed. I fixed the leaks and was about to do the transmission flush this upcoming weekend. However, My girl was driving it today and got the infamous p2004 and an associated p0173 and p0170. I inspected the intake runners, internal and external and all linkages are intact.
i also started the car and at idle I could see all the runner valves were not getting vacuum or pulling in the internal or external runners, my first question is do these runners close under idle conditions?
I also checked all vacuum hoses associated with the assembly and checked the vacuum electronic actuators ( pictured below ) by energizing them with 12 volts and watching them actuate.
every vacuum valve holds vacuum and there’s no cracks or bends in the linkage, my next check would be to see if the electrical connectors to the electronic actuators have 12 volts, is there a common ground between both actuators? Or a common electrical fault that causes this condition?
The more the throttle plate is open the less manifold vacuum. I know for certain the center actuator cycles in (toward the vacuum bell) when the car is at idle because I just did the lever repair on mine. I didn't pay attention if the outside 2 cycle in at idle but if the solenoid control logic puts vacuum to them they should retract as well. If nothing is happening it sounds like you have a wiring issue that is common to both solenoids. I don't know if 12V or ground is the control side, maybe someone with a manual or experience can chime in.
The more the throttle plate is open the less manifold vacuum. I know for certain the center actuator cycles in (toward the vacuum bell) when the car is at idle because I just did the lever repair on mine. I didn't pay attention if the outside 2 cycle in at idle but if the solenoid control logic puts vacuum to them they should retract as well. If nothing is happening it sounds like you have a wiring issue that is common to both solenoids. I don't know if 12V or ground is the control side, maybe someone with a manual or experience can chime in.
that’s what I was thinking sadly wiring schematics are hard to come by without paying money. Might end up being worth it in this instance.
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