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BodybyFisher posted a topic in Cadillac Deville, Eldorado, Seville, Fleetwood, Sixty SpecialProblem: Fast idle, about 1,200 RPM in drive and 3,000 RPM in Neutral. Intermittently at first, first time was a surprise. Historically I know that on the pre-1996 Northstars, this is due to the ISC Motor or Idle Speed Control. Our friend and member @Barry94 did a terrific write-up back in 2005 that has always been helpful in understanding and diagnosing the ISC motor. This thread was a walk down memory lane for me. So many members I had gotten to know in this thread, that contributed so much to making caddyinfo the terrific resource it is, their help and knowledge is preserved in threads like this, I miss them all. My name in this thread is Scotty (retired). Barry's outstanding writeup is here: Removal of the ISC motor was a lot harder than I recall from 91 Seville. There are three nuts to remove it once the cruise control servo is removed, one of which is difficult to get at. If I had a throttle body to intake o-ring, I would have removed the throttle body to make it easier. Important TIP, never remove the throttle body without having a replacement o-ring on hand. Once you remove the throttle body, the rubber O-ring expands SOO much that it is unusable and cannot be reinstalled. The heat, fuel and oil must swell the rubber and as long as its contained, all is good, haha, but remove it and its like a Jack in the Box or Can of Snakes, bam, now too big to go back... don't ask me how I know that Here are the parts disassembled, it was terribly dirty, the grease was dried out and the unit was very worn out. No doubt this is either the original, or it has done its job well for a very long time. Other than being very worn, I didn't see anything that would have caused my high idle, the closed throttle contacts looked good and tested good with an ohm meter. But the commutator was worn very bad, it had sort of a valley worn into it from the brushes as seen here (bad photo, I know, sorry). This is an interesting motor in that the commutator is oriented as a disk or turntable that the brushes skate on verses the typical motors we are used to where the commutator is a rotating cylinder with the brushes from the sides. Badly worn washer/ring, grooved Stator and magnets. The 'bearing' at the bottom was dry and sticky. Two brush holes, note spring stuck in hole, I had hoped that this was my problem that the spring was not supplying adequate pressure given the commutator wear. In actuality, that might by the problem here, the commutator turntable was worn so badly that there was a groove, that groove causes the brush to apply less pressure as the spring is less compressed and the brush sticks out further causing less stability in the brush. I don't think this ISC is salvageable. Gears gummed up I didn't have a whole lot of hope that I could fix this unit given the wear and that I didn't find a problem besides the bad wear. This unit owes the owner nothing. But I cleaned it up really good, lubed it up and reassembled it. Getting that lower nut on is NO fun, good thing I have the dexterity of a brain surgeon but make sure you cover the area below the nut, if you drop the nut, kiss it goodbye, it ends up down by the steering rack lost forever (don't ask me how I know that its an M5 nut ) << hands of a surgeon? No good.. engine still racing today intermittantly. Ordered new one from Rockauto, arrives tomorrow. To be continued. Its time for a new camera