Okay here goes. I have owned this car for about 3 years. It always idles at around 1200 RPM until you put the defrost on and then it will go down to 1000. I only drive it two or three times each summer as I'm busy doing many things. I just bought a low mile 380 out of Florida last week. I got tired of all the little issues with the 81 and figured just get a newer better one. So I have been driving it a lot the last few weeks. Tonite as I pulled up to my gate and put it in park, the idle suddenly went down to 700 which is normal. So I think I can discount the possibility of the over voltage fuse(relay) being fried. So I am wondering could it be the 02 sensor, the temperature sensor or sticking throttle linkage. The accelerator has stuck wide open several times in the past. Something I read about in one of the threads about a plastic part on the firewall where the accelerator pedal linkage goes through to the engine compartment. I'm stumped and was wondering if somebody could weigh in on this and maybe enlightment me a bit on what possibily could be the problem. I checked the vacuum lines many times and there doesn't seem tobeing any vacuum leaks that I could detect. I even used a vacuum leak tested device from a professional mechanic and couldn't find a problem with leaks. I know there are a lot of very knowledgeable people in this site so I am hoping someone can offer some ideas.
81 380SL
85 380SL
94 Range Rover
07 Harley Davidson Street Glide
1955 Harley Davidson Stock FLE

This is almost always the idle speed amp that quits working. I can get a rebuilt one for you.

Thanks Dan. I will pass this on to the new owner as I just made a deal to sell it as soon as my other one comes in. I will pass your web address on to him as it has a few issues and he will need parts and you seem to one of the most knowledgeable people on this site.

Yeah, you need a little plastic ball that has holer in it. The throttle linkage shaft goes through the hole and the whole assembly is held in place by two pockets that hold the balls ( that suddenly sounds pretty funny )

At any rate these are cheap parts and almost every car will end up needing them eventually. You need two balls and two smaller tubes that fit inside of them.