You'll want to soak the ICV overnight in something like WD40 or liquid wrench to really get the thick gooey junk out of it. The fluid will also lubricate. For best results, cap one end with tinfoil and rubber bands, then fill the whole ICV up with fluid. Dump it out the next day and you may be surprised at how black the fluid is. Be sure to blow it out with air.

The little shutter inside often gets stuck with crud and will not allow the proper amount of air to be metered. When the hoses to/from are brittle, they also allow unmetered air into the system which roughs up the idle quite a bit.

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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