I've searched a lot of threads on this subject. My 420SEL has a 1000-1400 RPM idle all the time. I cleaned the ICV and it resolved the idle issue for about three start-ups and then it went back to normal at 1k. I then disconnected the cruise control thing at the front of the engine and then the idle went to normal for about three start-ups and then back to 1k again. I can feel the ICV vibrating when the ignition is on so I assume it works. I looked over all the linkages and everything looks to be normal. Is there anything non-electronic to look for besides vacuum leaks that could cause high idle?

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual