As there guys are all rioght LoL ,m its all issues that have happened to many . Lots of times as have mentioned an issue is the Idle Speed Control Valve , ive seen it 2 times on my VR4 and on many other we have worked on. The valve either is working erratic or not at all , and the ECU is doing it as a remedy to try and drop the RPM and "trigger" the ISCV (IACV intake air control valve) to drop the rpm to the recommended range for the operating temperature. Also as stated a vacuum leak can cause the idle to be a little higher than normal , thus the ECU does the same procedure to remedy it and also trigger the ISCV causing teh rpm to flux . Check the PCV vacuum hose and see if its leaking or broken , also the vacuum hose leaving teh intake going to the brake booster and lastlly teh one going frum the intake to teh fuel pressure regulator , on some occasions the diaphram in side teh pressure regulator was busted and teh intake was pulling in fuel into teh intake plenum frum the fuel pressure regulator