High Idle On Ls400 (not Tps)

[Banshee365]

Hey guy's, just did a tune-up on my mothers '96 LS400 including: plugs, wires, caps, rotors, coolant, trans flush, and TB cleaning. The TPS has not moved and after a while the engine idles at 650 on the money. But when you first start it and even after 15 minutes the car seems to idle very high in gear, very close to 1k rpm. I am thinking it's related to the computer, since the battery was unplugged. Is there a way to reset something to try and get the idle normal? She's complaining to me that she doesn't even have to hit the gas to go in gear, it accelerates almost on it's own. And she has to hold the brake alot harder to keep it stopped at a light/stop sign. What do yall think it could be, the TPS is still on the factory mark. When she pulled into the garage today I started it up and it idled right on the money at 650 rpm. Thanks guys!

-Kelly

[93ls400walt]

Could be many things but I would go over what was recently done. Like look at the throttle cable to see if it is binding, ect. Look into the throttle body to see if the throttle plate is closing properly. The repair manual list in the Matrix chart the flow of high idle problems, in order of causes , #1 switch condition signal circuit which includes the Park/neutral switch signal, Air cond. switch signal and the TPS. Next is the IAC valve then the A/C signal circuit. Since this was not a prob. before. I would go over what was just done. Also the Dash Pot, in my thought, could affect the idle.

[92Lex]

I'm not sure what the exact problem is but it's normal for cold engine's to idle high. Automatics also tend to "creep" because they are always in gear.