85 380SL, 76K miles
When I start up and drive it idles is about 600 in neutral and it runs fine. Runs great at speed cold or hot. Sometimes (and it seems to be intermittent but more often than not) once it gets warm, the idle in neutral is about 1500 rpm.
It only idles high does it when it is hot.
Any suggestions as to cause and the fix.
Thanks in advance