my car goes from idle to about 1800 rpm and back down over and over, have replaced my iac and tps but still does it. sometimes it will go up to about 1800 and stay there for about 30 sec and then up down again. 3 mechanics cant figure out but two of those wouldnt even look at it. any ideas?

Look for vacuum leaks.

intake manifold or vacuum use a can of carb cleaner (sparingly to find vacuum leaks) a small burst near a vacuum leak will change your idle speed pointing the way to the leak

these cars have a fast idle valve, if they start leaking as they do over time they will do that exact thing the other thing to look for is if the throttle cable is adjusted corectly it should not be holding the throttle plate open at all when its at rest and the base idle using the screw thats in the top of the throttle body one of those 3 will fix it l promise