whenever my car is idle for about 1 minute or more, the engine starts vibrating unusally and it sort of seems like it will turn off and die or something (except when warming up the engine) and whenever im driving on the freeway at about 60+ mph, the engine will make sounds like reving that will go up and down like its struggling to keep up with the speed or something, even when i use cruise control and im not going up or down hill. there is also this odd exhaust smell from my car which other cars dont have, my brother agrees too. my brother told me that there might be a bad fuel and oxygen mixture so im assuming that its the oxygen censor, right?
my car was tuned up about 1 year ago and the oil was changed about 500 miles ago with mobile one synthetic oil. i cant seem to think of any other reason for this

 

You will probably be able to get a better response if you posted this in the general tech help section.....

Sorry, I don't know enough to answer your question.