Every one who have a 1994 850 Know there a upgrade kit for the knock sensor 143 is the front sensor.. it coming due to the dirty connection..

You can disconnect it and clean and reconnect it again but the code will come back later..

the upgrade kit cost $140 I think may be $90 can not remember but it come with 2 sensor front and back....

many will tell you that you can replace it without remove the intake manifold... well personly I don't think it is possible...

I do the up grade myself it take me a good weekend.. but now looking back I could done it in 1 day....

but here is the problem after I upgrade the kit 1 month later code 143 is back again... and been on since than.. the fix was a wast of time and money.. but I tried.....

You can do it yourself it not that hard it take a little time and patient

you also need a new intake manifold gasket $10

O-ring injecter I reused them all clean them up and put some vasiline on it work fine no leak...

Hope this hepl..