ok i have all the typical signes of a bad ks. but i just went to extract the code and it didnt come up, infact no codes came up it said it was clear. but before i extracted the codes a while ago and i had a bad o2 sensor and now it says i dont... i think i got the knock code too before but i dont remeber. does this happen often or what the heyl is going on. this is making me kidna mad cause my car is dog slow pretty much off the line it used to be faster. but o well i guess, if anyone has any idea why its doing this please help me. thanks