revving engine

[Y33TREKker]

I know I asked this once before but can't find old thread.
When in park my engine is revving up and down, 1000rpm-3,000 rpm
What part needs to be replaced?
Thanks

Maybe your IAC (idle air control) valve needs replaced? Or simply cleaned.

[KRemo]

My VX did it and nobody could figure it out. I replaced idle air control and kind of worked but started again. finally I replaced the idle air control wiring and it fixed the issue.

[89Vette]

Vacuum leaks (intake manifold leaks) often cause this too...but you should be seeing a code for that.