I started my 850 R yesterday morning and it took it a good bit to start and when it did it barely started and then went up to idle. I went back inside to let her warm up when i heard the revs go way up and just hold there. I walked outside and it was holding at about 3500 RPM. I shut it off, waited a sec and tried to start it and it wouldn't turn over. I got it started after a while and then it was fine for a sec then the revs went right back up again. It did it a few times yesterday and once again this morning. I took it to my friend and we put the scanner to it and the oxygen sensor was throwing a code saying that the car was running too rich. I've checked a couple of sites and some say it's a vacuum leak somewhere. Anyone else heard of this?

 

it was the coolant temp sensor....mine the the same thing, it was running fine and all of a sudden - the exact same symptoms you mentioned happened. guess the sensor shorted to ground so it must have though it was REALLY cold.

 

^^^ This sounds logical. If the sensor goes, it will make the car run very rich because it is trying to warm up the engine. I would have thought you would have had a code for the coolant sensor too.

I would check for vacuum leaks first, and if everything looks good there, then replace the coolant sensor.