simplest think is check all the cars fluidis , , The check engine light . get a on sale oil chage , eswpecially since if your due for one, reson oil filter coukld be malfutioning or if it is a new filter could be maluftion. For 12.00 oil change these procese of testing eliminating problems cheap.  . use got octane gas in your car i get rid of engine knocks. and after the oil chage see if the litle still goes on and off,  you may have to have car put on computer dx test. thats expensive. Check your oil level also, the computer dx machine varys $70.00 to $120. so the above are worth checking prior to doing the computer dx, which stilll mite not find problem, does your car exhust smoke?