"Is it OK to push the plate down and spray a good dose of carb cleaner in there?"

Probably, but the bottom of the plenum is rubber - make sure the cleaner will not harm that. I used rubbing alcohol on shop paper towels, pushing down the vane and thoroughly cleaning the inside of the venturi and the contacting edges of the vane. Do this with the engine off - it will immediately stall if you try it with the engine on, and you don't want to be there if an intake backfire should occur, anyway.

Removing the distributor/airflow meter unit isn't too difficult or messy, and the rubber plenum can then be removed for complete inspection of the mechanism. If your idle circuit hoses are old, why don't you replace them and the rubber plenum at the same time as the regulator, and it will make this operation just an extension of that repair. Order the saddle that holds the rotary idle air valve too, as it gets hard and brittle and difficult to remove non-destructively. Aftermarket, none of these parts are very expensive.

Steve

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'91 MB 190E 2.3
'08 RAV4 Ltd 3.5
'83 Lazy Daze m'home 5.7