My buddy has a 98 lego 2.2, he is having similar trouble with his car as I am, can the knock sensor go bad without throwing a code, or start failing without the code?

its always possible for it to go out and not throw a code. it should tho. if its bad your timing will be retarted i think 8 degrees. that is one way to check.

they can and will go bad but they will eventually throw a code, mine did. but it really isn't worth driving around for 2 years with crappy power and gas mileage? waiting for it to code. o2 sensors are the same way, i think.

 

how many miles? over 125? and i think you are due. it's a 50 - 60$ part that lasted 125k miles. it has done it's job, time to get a new one.

yes it's possible. doesnt' make any sense but i've seen parts cause driving issues but no CEL.

 

i'd troubleshoot/diagnose here or with someone who's good at this stuff first before just guessing though. all sorts of things can have similar symptoms.