Why does your suzuki sidekick rev up and down when in park?

If your Suzuki Sidekick is revving up and down while in park, it may be due to a vacuum leak, which can cause irregular air intake and result in unstable idle. Another possibility is a malfunctioning idle air control valve (IAC), which regulates engine idle speed. Additionally, issues with the throttle position sensor or fuel system could also contribute to this behavior. It's advisable to have a mechanic diagnose the issue for proper resolution.