98 SL2 idle/ stall problem???

I have a 98 Saturn SL2 with 157000ish miles on it. Just recently i will have to hold the gas peddle in while cranking the engine over... it will sputter a bit till it starts (almost like its clearing it out). its idling at about 1100R RPMs and will spike to around 2-2500... then i will back out of my drive way and put it back into drive it will drop RPMs to almost a stall... I have to put it into neutral and the RPMs will spike again to 2500 then drop back down, then I can put it back into drive! Sometimes I can take off sometimes it will start to stall again! and ill have to go back to neutral.... Any Ideas??????

Diagnos in this order:

-Change your Engine Coolant Temperature Sensor. Yours is resin and gets eatin thru by the coolant sending false data to the PCM. The new ones are brass and will last the life of the car. The sensor is VITAL to many systems including:fuel management, air/fuel mixture, idle speed, fan control, shift points, TC lock up points, etc
-Change your spark plugs. NGK Coppers are best. Nothing fance. Simple is better
-Clean your throttle body out. Make sure the passages (especially those to the IAC (idle air control) are clear)
-If high idle still continues, tap the Throttle Position Sensor with the end of a screwdriver. if the idle changes, replace the TPS