I have been trying to track down a bad idle problem forever now. I have replaced the AICV and the FIVC and still the idle rises to about 1700RPMs and then drops to 1100RPMs and repeats. Sometimes there is never an idle problem and the car runs just fine. Every once in a while the car changes its mood and has a faster repeat of the idle and it varies between 1400 and 1200 RPMs. When it does this the car lurches when driving at a constant speed between gas on and gas off. I just cannot figure out what could cause such a weird problem? EGR? I am attempting to check for faulty wiring but I am not really sure how to check.

 

hope you find the solution soon. Have you looked at faulty sparkplug wires? how about plugs? PVC valve leaks?

 

check for vacuum leaks, and bubbles in your coolant, sometimes it will do that if the idle is set too high or too low also