Hello everybody! Everyone has been immensely helpful with my car so far, and I cannot thank you enough! But now, we are at the most dreaded job of all: the knock sensors

ive had a restricted performance light on for the entire time I’ve owned the car, and a knock sensor engine code along with it. My biggest question is, do the XJR and xj8 have different knock sensors? I found two different kinds online, one with a ring, another which seems to be more of a plug. I’m unsure which kind I need. Also, since I have to remove the supercharger to get to these, any help or work guides for this job or for taking off the supercharger would be a huge help!!

 

Yes, the earlier type were a different fitting, I forget when the changeover took place. Maybe strip yours down and see what type of fitting you have.

Either way Rock Auto has some good prices, somewhere around $60 buck right now.

 

The AJ27 uses a 'donut' style KS. The AJ26 uses a KS with a threaded mount.

SU7015 is the generic part number.

 

Your gonna want to change both knock sensors and torque them down with a click type torque wrench. I don’t know what the torque specs are for those but it’ll be around 13 ft lbs. Find out first for sure!

These next steps are preventative maintenance that I would highly recommend doing because it’s so much easier with the charger off.

The next thing you’ll want to do is replace both heater hoses under the charger and the plastic 3 way tee located under the throttle cable where it joins the throttle body.

I would also replace the fat J shaped coolant bypass hose in front of the supercharger along with the large O ring under the 3 bolt aluminum housing.
Make sure you get 2 replacement O rings where the aluminum thermostat housing bolts to each cylinder head.

Nows a good time to change out the supercharger oil. There’s a small Allen screw in front that you’ll have to either suck out or somehow stand on end to drain. I’d refill the charger oil just sitting back on top of the engine so it’ll be level. I’d also put Teflon tape on the threads of the oil fill plug just to be safe.

The last thing that I can think of is a brass/plastic retainer for the vacuum brake booster where the plastic pipe goes under the throttle body on the passenger side. You essentially buy the brass piece assembly and you can carefully remove the plastic retainer and there’s a special size O ring in there. Those 2 pieces get cooked and cause vacuum leaks when they’re disturbed.

All this information is just to get you ready for what’s at hand.
Good luck!

 

The two sensors are not interchangeable.