Same problem here, though the slight idle stumble goes away when the engine warms up. I think. Maybe a split vacuum line that closes up with a bit of heat?
I wanted to clean the idle control valve too, but where the heck is it? is there an online manual somewhere that details this operation 'cause I couldn't find one.
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91 Mercedes Benz 300TE
04 Honda Element
86 Honda NS 400R
Could be a number of things. Had rough idle on my 89 300E. I changed wires and plugs, oxygen sensor, cleaned fuel injectors, changed fuel filter, replaced motor mounts, cleaned ICV and replaced OVP. Each change improved the idle till it was finally cured. That was about 15,000 miles ago. Runs so quiet at stopliights now, that sometimes it's hard to tell the engine is on.