Revs upto 4000 rpm in idle and while driving too ! all by itslef.

run the fault codes
check for vacuum leaks on all vacuum hoses
check fuel pressure
use quality injector cleaner

When was the last time a full tune up have been done? A bad intake gasket would do that.

Trans is slipping, is it not?

Has to come out & be rebuilt

Check for a possible leaking vacuum system, maybe the vacuum booster is leaking, that would explain the idle being affected by stepping on the brake pedal.

I would replace the fuel filter(every 35000 miles),check the condition of the air filter and check out the catalitic converter and feel the tail pipe to see if the flow seems clogged and weak when some one else gives it the gas.
My 2001 had to have a new cat at only 44000 miles. I had them install a "High Flow" type.

THERE IS A TEMPERATURE SENSOR ON MOTOR WHICH CAUSES THIS PROBLEM... USUALLY IT SHOWS A NEGATIVE TEMP READING WHICH CONFUSES THE COMPUTER CAUSING IT TO REV UP....HAVE THE ENGINE DIAGNOSED ON A SCANNER....GOOD LUCK...

Sme thing happened to me, but the advice is grim. I had to have the whole transmission replaced because of a bad torque converter...I would be sitting at a light and the car would just go all by itself, or as I was driving down the highway the tach. would go crazy and shut the car down into "safe" mode where it would not go out of first gear. Other times I would have to keep both feet on the brakes because the car would be pulling so hard! The dealership told me the crankshaft position sensor too, then a month later the car just shut down and would not start. Hope this helps.

Hi    try this  switch on ignition without starting depress gas pedal fully and hold down for a second or    two then start the car and lift up your foot slowly when it fires. sometimes this will reset ECU    let me know if this works

hey-I have has this before different car but same - idle control valve is failing - computer at shop will pick this up on diagnostic