I have read through old posts on high idle and could not find one that matches. My 87 300E out of nowhere started idling at 1500. At times she will surge from 1k to 1.5k. Sometimes she will back down to 500 where she normally ran and surge back and forth to 1.5k. I do not have any performance or cold start problems and this happens from the moment she starts up. Makes no difference whether she's cold or hot. I am not that familiar with this engine as I recently purchased the car. I did check the fuse on the OVR and replaced it though it metered fine. I also read in an old post that on an 87, the idle would not be high with a bad relay. HELP! Where do I start?