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What are the procedures for replacing the knock sensor? i am also getting a code for a "can purge thing"???? how and where do i get one of those?

knock senor is pretty straightforward. Not sure if on the turbo models they are in the same location but on my N/A it's on the back of the block driver's side by the intake manifold. IIRC 12mm bolt holds it on Super easy.

1991legacyturbo wrote:What are the procedures for replacing the knock sensor?

Unplug old sensor
Unbolt old sensor
*Optional - use sandpaper to clean mating surfaces
Bolt new sensor on
Plug senor in
Drive away.

all subaru knock sensors are in the exact same place so far, super easy to do, easiest 1hr to get at work when flat rate!

hey thanks guys. do i have to drain my coolant to do this?

The knock sensor has nothing to do with coolant. It simply bolts to a threaded, dead end, hole in the block. Make sure you are getting ready to remove the knock sensor and not the coolant temp sensor.

some engines have the knock sensors thread into the block into a coolant passage. it's that way on my LT1. Maybe he assumed that was the case.

ok thanks guys. the reason i thought you had to drain the coolant was because my hanes manual said something about draining the system.



The purge cannister solenoid??? where do i find these and how hard are they to replace?

When replacing the knock sensor, the fsm says to install the sensor with the wire going out at a 45* angle. This means if the passenger compartment is 12 o'clock and toward the radiator is 6 o'clock, the wiring coming out of the installed sensor should be at the 10:30 position.

I don't know the technicals as to why the fsm says that but here's what happened to me: I installed a new OEM knock sensor with the wire coming out at the 2:00 position because it was easier to connect the male and female plugs together. But my engine kept pinging and sometimes knocking. I read the fsm and followed the instructions for the 45* angle wire placement and the pinging and knocking went away.

Took me all of 2 minutes...maybe 1.

The cansiter purge solenoid is tricky to get to. if you know where it is, you can try to get at it.
I, along with a few others, have just left the bad one in place and plugged the 2 vacum lines and the wiring clip in to another sensor and found a place to put it. It can be a real pain to get to in it's stock location. (Under the intake runner behind the PS pump)
Replace it, and reset the ecu (possibly not necessary).
if you do a search, you will find a thread entitled "canister purge solenoid - fixing the problem" it has a nice picture of what it looks like if you're unsure.

I was getting the same code, and you know what the problem was? My gas cap vent was plugged. It was building up too much back-pressure in the fuel system and throwing a code 35. As soon as I would take the gas cap off and release the pressure, the CEL would turn off.