Celica 1600 GT Idle problem?

[Elkjaer]

Hello, I'm new in here, and i hope somebody could help me fix my problem, I got a 87 Toyota Celica 1600 GT, with a TVIS 4A-GE engine in.
My problem: when i just start the engine cold, it revs to 2500 RPM, and stays there for 1-2 minuttes and then falling to about 1500 RPM, and when the engine is completely warm my idle is about 1000 RPM.

first i think that 2500 RPM cold is a bit to much, and i dont know what to do with it. but my biggest problem is when the engine is fully warmed up, and i rev it to lets say 3000 RPM and then lets the gas of, the engine falls to about 500 RPM sometimes it stalls but if it not stalls then it would slowly gain some RPM and then it goes up to 1000 RPM again.
How can i prevent the engine falling that much when i let the gas off? it's quite anoying when i drive the car and comes to a stop it sometimes stall, :/

Cheers, Danni

(i hope you understand my bad english, i'm from Denmark)

[alltracman78]

Your ISC valve is probably sticking.
You can replace it with a new one [expensive] or try removing the old one and cleaning it up.

Older Toyotas normally idle very high when cold, 2500 RPMs sounds normal to me if it's late fall/winter in the north.

[Elkjaer]

that was also one of my thoughts.
Can i test the isc valve, to se if it works. i remember i read that i could cover the big hole in my throttle body when the engine if warm and there should be no vacuum? is that right?
But is there any guide, how to clean it. And would i need any new parts? gaskets or something?

i should maybe say, when the rpm has been down to about 500 and it goes up to about 1000 again, it stays at 1000 until i rev the engine again