really high idle

i have a 90 240 with a sohc ka. it idles at 2500rpm then drops to 2000 then raises to 2500,it repeatedly does this. the engine is completely stock. i removed the aiv, welded the hole where it connects to exhaust pipe, and plugged the vacuum tubes mounted on the intake manifold where aiv hoses connect to. some other things i did that should probably be put into consideration. i tore the motor down to the block to replace all the gaskets and seals because it was leaking oil. the gas in the tank is about a year old. upon startup the speedometer pegs itself. any help would be greatly appreciated

i think u should expect somekind of gunk/buildup after a year withouth running it once in a while....

intake side vacumm leak

found the vacuum leak and the tach stabilizes at 2500rpm. i adjusted the idle adjustment screw completely clockwise and rotated the tps sensor forward slightly to drop the rpms it was a success(1400 rpms), but i looked at the timing and it was way to advanced.i adjusted it to specs. yet it still idles high at 2500 rpm. even before the vacuum leak was fixed i adjusted the timing to specs. any help would be greatly appreciated. thanks

Vacuum leak.

Look around. I had the same problem except mine was at like 1500. I had a sliced vacuum line.

Also once, my alternator was very loose and it made me have about a 1500 RPM idle. The ecu was trying to make up for the low voltage coming in and was kicking up the idle

As previously mentioned, check for vacuum leaks. Air entering the intake manifold or elsewhere after the MAF sensor will cause a high idle. I'd also check the idle devices the sohc ka uses to maintain idle ala a Nissan FSM.