2000 Nissan FrontierMarch 28, 2015Truck idles to 2500 rpms and then to 1500 rpms continiously. What is causing this? Keywords:Frontier 1 thought on “2000 Nissan Frontier” Freeautomechanic March 31, 2015 at 9:52 am A higher than normal idle is generally caused from a vacuum leak. With the engine running, try spraying some brake wash around different areas of the top of the engine.(stay away from the exhaust). Listen for engine rpm change and then concentrate on that area looking for cracked hoses and or right around the intake gasket area. This should help narrow down where it is coming from. Comments are closed.