I am in the process of replacing the intake manifold and I am wondering if I should replace the knock sensors while I'm at it. Are they a common thing to go bad? Anything I should do while I have the intake off? There was some oil in the valley, what causes this? Thank you for the help. -Josh

 

Forgot to mention car has 82k

 

What car do you have first off? And I haven't really heard of the knock sensors going bad on the M272/M273. Don't think they do either on the M113k if it's an E55 that you have. Have you done air filters while the intake is off? Lol

 

Knock sensors should rarely ever go bad. No need to replace it. I've had a knock sensor code pop up once in conjunction with a bad ignition coil, replaced coil and knock sensor code never came back.

 

^Same, knock sensor codes have all been related to failing coils for me. $59 at Advanced and 15 minutes of work later it will be resolved.

So, if you have some extra cash, and you have a high mileage car, I would consider doing ignition coils actually

 

Thank you guys for the replies, I ended up not replacing them.