96 monte carlo unexpected acceleration

hi, my nephew has a 96 monte carlo 3.1 and from time to time it will take off when you are at any stop light or just in traffic, the car will accelarated itself and your force to ride the brake for fear that it will do it . what do you think it could be the problem. thanks and also his interior lights are not going off ,when you close the ddors and adjust the dimmer switch, his driver side door its having a problem with closing propertly, its the switch that controls the interor lights built in inside the door latch? i could not find a switch around the car frame or in the door to see if its working .thanks

im having the same problem wit da acceleration , did some reading and in my case i believe my upstream oxygen sensor is bad whitch in return its giving my PCM bad signals whitch gives other sensors bad reding like the THROTLE POSITION SENSOR. 2morrow im replacing my OXYGEN SENSOR ill let you know how it turns out. I bruoght a haynes repair manual from auto zone and was surprise how much i learned from CHAPTER 6 EMISSIONS on sensors & pcm whitch controls acceleration and so on. BEST OF LUCK TO Y'ALL PROBLEM

Start by removing the intake duct and MAF, and thoroughly cleaning the throttle body, throttle plate (on both sides), IAC air passages, and remove and clean the pintle on the IAC.