my 1990 accord with auto transmission runs fine in park when its cold. As soon as the engine warms up it starts to rev up and down. This only happens in park and neutral. when in drive it runs great. anyone have any ideas. thanks jim

 

Vaccuum problem, probably your MAP sensor. When your car is cold, the engine idles at a higher RPM and that's why it doesn't happen when it's cold.

 

my car does the same thing, the revs go up and down but its only in the cold.what i do when it does it i hold the gas a bit till it ildes down to 0 rpms

 

yeah map sensor go pretty often