It seems that my 1990 Ls400s motor is too reved up when I first start the car in the morning, I also hear the radiator fan going at full blast, when I drive it for a littlebit it goes down, but it still seems a little bit too accelerated, might the timing be off, or what could it be? Also when I turn on the A/C the engine sounds louder, and when I shut it off the e is like a small thump and I could feel it.

 

The ISC motor is stuck. The ballbearing in the shaft need replacement, or cleaning. WD40 works great

 

I think lexold made a typo, it's "IAC"

 

it's always been known to me as an ISC personally. then again around here I also see the check engine light referred to as an "MIL" which I personally connect more closely to "mother in law" than "malfunction indicator light"