I have a 97 monte carlo that will idle above 2500 rpm when I start it. It doesn’t do this every time and the length of time varies. Doesn’t matter if it is a cold start or not. Temperature outside isn’t a factor. It will idle fast in the summer and in winter. The length of time varies. It has gone all the way to work, practically pulling me when I try to stop or sometimes I can immediately shut the car off and restart it and idle will be normal. Most of the time I can drive the car to the end of the block and when I come to a complete stop at the intersection the idle will suddenly drop to normal. I replaced the TPS sensor but that didn’t help, now I have no idea what is going on.