My car has 114k miles on it and has a hesitation. There was a faint hesitation a while back. I figured it was the 2 sensors so I replaced them. That was when I realized that there are four of them. The faint hesitation had not come back and since I could not get to the other two I put replacing them off for a bit. I changed the plugs at about 100K. I was thinking that the hesitaion was coming from the O2 sensors that I didn't replace. I was told that if the O2 sensor was causing the hesitation that the check engine light would come on. It has never came on. Is it possible that the sensors could be bad with out throwing a code? I was thinking that since there are four of them that it might be possible but I don't know how the on board comp. interperates the signals from them. I will probably be paying someone to replace these two sensors but was wondering if the hesitaion could be from something else that I wouldn't have to pay someone to fix since I do most of my own maintenance and would hate to pay for something that I could do myself.
Any information would be greatly appreciated.