I have a 1992 Camaro RS 305 TBI Auto< with 86000 original miles. Car is all stock. my car has been running fine up untill i took a 200 mi drive in it last week it ran fine on the drive avrg. 21 mi a gallon, then the next day when i started it up the idle was jumping from 400-2000 rpm the jump up and down is very consistant but it goes away and runs like a champ after it warms up. so i replaced the IAC valve and the problem went away... for 12 hours. next day same story. but now when the cars rpm's all jumping and you hit the gas there is no response for about 5 sec then everything catches up to itself and the car revs fine once off the gas back to sporadic idle until warm. its been 3 days and for the first two the car had to sit for hours and cool completely off for the problem to exist now its only has to sit for maybe an hour and it will do that. also smells like it running rich. i have checked for vacuum leaks and shorts and have found none, i rely on this car as a DD so i need to fix it before it totaly craps out, ive found a few posts with similar probs but no solutions and i cant afford to play the part guessing game. i have a multimeter to test but not sure what test and on what setting besides the obvious things like alt and batt voltage. PLEASE HELP

 

Also i will be changing the O2 sensor tomarrow to see if that helps