its an na motor i got the tps adjusted a month ago and it idled perfectly at 750 than couple weeks ago it started to only idle at 750 when i turn the car on. but if i start driving it wont idle underneath 1500 it stays constant at it. can anyone tell me what the problem is? and this is something different i checked my intake arm theres a black stopper thats moving back and forth is it suppose to be there or is the intake tube suppose to be empty? thanks for your advice