84 380SL Fast Idle
 

We have a 1984 380SL. The problem started last year towards the end of the season. Since we live on the beautiful North Coast of the States "Euclid, Ohio" we only use the 380SL in the warm months. We expect to see some warm weather by the end of May. None the less the 380SL sits all winter long under cover. The problem seems to be that once the engine is warm it will go into a fast idle condition. It will just sit there at 1500 RPM for a while and then sometimes it return to normal. You would think that it would change from fast idle to slow once it warms up but the condition seems to be just the opposite. I removed the air cleaner and checked for a vacuum leaks but everything seems to be good. Any suggestions?

You should have an idel air bypass that allows for more air to bypass the throttle body. If it is stuck open the car will start fine and as it warms up the idel will increase. I'm not shure where it's located on your vehical or how to test it but you also need to find out what controles it and test that as well. It may be something simple like a wire off a water temp sensor.

Good Luck
John Roncallo