I would clean your ICV with brake cleaner and lube with WD-40, then check the hoses for air leaks and replace if necessary. Pop the hood at night when it is pitch black and see if the wires are arcing. Check out my experience: http://www.peachparts.com/shopforum/showthread.php?t=162549&highlight=wires+arcing

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08 W251 R350
97 W210 E320
91 W124 300E
86 W126 560SEL
85 W126 380SE Silver
85 W126 380SE Cranberry
79 W123 250
78 W123 280E
75 W114 280