I have a 88 560sec. I've had problems with FRP's and high idle. Because of the problem it doesn't get drivin as much as I would like.
I barely made it home the other day. Loss of power then died in the driveway. I replaced the fuel pumps and filter and that fixed that.
But I had trouble getting it started ( a recent problem when cold, probably the cold start injector). I took the FRP out and jumpered 30 and 78 sockets to run the fuel pump constant. After it started with some priming through the throttle body or what ever it is named it ran at idle really well. As soon as I put the FRP back in it ran with a high idle and some hunting.
I've had the high idle for a long time and have been trying to figure out why. I don't have vaccum leaks and ICV is good.
Anyway does the fact that it idled normal with the jumper give any indication of why it idles high with the FRP?