Please see post #8 of this thread. I have the socket and ratchet placed near it.

Please go over my sets of posts and the other hidden bolt location is mentioned there. Go over them more than once and you will find answer to your questions.

Do not bother with non OEM sensors. Sensors ... specially the ones that are deep in the gut are not an item to save money on.


Salim

 

Salim, do u have any recommendation on where to order OEM knock sensors or is Sewell your choice?

cheers

 

Yes, I did order from them. Make sure you provide them your VIN.

This thread still lacks a part list.

Salim

 

I replaced my 1999 RX300 knock sensors this weekend. The car has 228,000 miles.

Many thanks to Salim for the great write-up and pictures. It is a huge help to know the size and location of the hidden fasteners on the firewall side. I sometimes wonder if the engineers
high-five each other when they design something that hard to work on. I cursed them many times today, both for the miserable hidden fasteners and for a few of the electrical connectors that refuse to separate. Electrical cleaner helped a lot with these.

Also a big help to know the knock sensor part changed in August 1999.

I can't imagine how you can do this job without removing the wiper bay. Someone else wrote they did it in 3.5 hrs. It's hard to imagine that too.

I replaced both knock sensors, bypass hose, and the wire harness.
Since my gas mileage is poor (about 16.5 MPG) I also replaced plugs (much easier with air intake removed), PCV valve, and both air/fuel sensors.
Since I was draining the coolant I replaced the upper and lower radiator hoses.
Since I was dirty already I changed the oil too.
I think it took me about 10 hours.

Do take pictures and mark everything you disconnect with bright tape. It's easy to overlook a hose or wire when reassembling. They all blend together.

One odd note - I found a mess of cottony stuff right under the bypass hose. It looked like some rodent was building a nest.

Parts List:
Contact the dealer to get the build date. Mine was built in July 1999.

Lexus parts from Lexus of Pembroke Pines
89615-12040 Knock Sensor $138.61 (Sensor in use up to 8/1999) Car has 2 of these.
82219-07010 Wire harness $26.50
16261-20010 Bypass hose $13.02
12204-20020 PCV Valve $6.02
16571-20030 Radiator hose (upper) $21.52
16572-20030 Radiator hose (lower) $24.46

From Rockauto.
Denso 3297 Spark plugs $6.30
Fel-Pro gasket set MS92766 $49.79
NOTE: Does not include a gasket for aft of the throttle body. I had to reuse the old one.
Coupon codes readily available

From AdvanceAuto
Denso Air-Fuel sensor 234-9009. They list it for $163.99.
Order on-line, apply a 30% coupon to make it $115.46, then pick up in store.
Current coupon code is TRT30
Borrow the sensor socket tools. They take a deposit, you get it back on return.

 

Cross bar right above the air intake. Don't see how you can do this job without removing the wiper bay and this bar.

 

Location of the hidden fasteners.

 

Finally there. I did not fully remove the intake manifold - just moved it out of the way.

 

The bypass hose and my rodent nest.

 

Knock sensors visible with bypass hose removed.

 

I just replaced mine yesterday. I did wire harness, bypass hose, both sensors, and the spark plugs. I removed the wiper tray as well. The bar stress bar wasnt in the way.

I discovered the sensors had been replaced atsome point with cheep ones (that failed) , they did not replace the wire harness it was brittle and the plastic holder was broken, I found a cigarette butt under the bypass hose....

I wish I could have obtained my parts as cheaply. The dealer wanted $212.00 each for the sensors. I got them from FCP Imports they had the cheapest overall price I could find when shipping is included.

Anyway it was not a technical job at all, just time consuming working in small spaces.

 

With the wiper tray and the bar removed, was easier to access the hidden bolts? Can you further comment on using the electrical cleaner to aid in disassembling the connectors?

 

Hidden bolt access is limited due to firewall. I had the cowl out and I found the access to be difficult.

Salim

 

It is definitely easier to access the bolts with the wiper bay removed. But they are still hard to get at. The cross brace isn't an impediment for the bolts. Removing it gives you more clearance for moving stuff around.

I find spraying electrical cleaner into the connectors lubes them up and makes it easier to separate them.

 

Hey I recently replaced mine but now oppose to just one sensor being bad both are now saying they are bad any suggestions

 

Both being reported bad may be the wiring harness.

When you did the job, did you replace the wiring harness too? When you put the wiring harness back on, did you attach that plastic clip that hold it up off the engine?