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RX300 knock sensor replacement DIY

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Old 03-02-10, 09:02 PM   #1
salimshah
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Default RX300 knock sensor replacement DIY

Difficulty level 6/10. Time 6-8 hrs

Tools needed:
Phillips screw driver, allen key, torx screw driver.
8,10,12,14mm sockets & wrenches
Assorted 1/4" 3/8" extensions and or adapters.
27mm wrench [I used adjustable wrench]
Torque wrench
torx socket
Trough to catch coolant.
3m Blue masking tape.
Marker/tags to mark where the hoses go. [if you rely on memory alone, you may be in trouble]

Material:
Knock sensors [take your vin number to parts as a switch was made]
Wire harness [most probably the old can not be reused]
3/4" high temp (gray) wire loom * [if your wire harness carrier box crumbles or is crumbling .. replacement with harness is over $1000]
coat hanger or stiff wire *
Lexus/Toyota coolant [I used conc red 1 jug]
2 Gallons distilled water. [you will need 1.25 gal approx]
Air plenum gasket set.
Shop Vac.

Other things to consider:
Since the top of the engine block is going to be removed, you may seriously think about changing the spark plugs and cleaning IACV.

General procedure: Slide a narrow socket over the pin end of the plastic hold down pins .. this squeeze the clips and you can lift the pin out. Loosen all bolts one or two turns instead of removing one bolt completely. Leave one or two bolts partially threaded and shake the component free. Similarly thread all nuts and bolts but do not tighten them down before seating (gently shake) the piece in. Then face evenly and then torque them evenly in criss-cross pattern. Always undo the most difficult fastener first and during assembly tighten it first. [for head gaskets work your way from middle to out during assembly].
Clamps on hoses should be moved over and clear across the barb. Twist each hose to break the seal before attempting to pull. During assembly gently twist the hose on. Make sure there is no twist/kink in the hose in its final state. Position the clamps in their original position (which typically is positioned to provide easy access).
All electrical connectors have a clasp to hold wires and provide slack and support. Make sure when you finish the job, you make no compromises. Inspect each hose/pipe/connector and replace them if you think they may need replacement.


1. Make sure the engine is cold.
2. Disconnect the battery.
3. Drain the coolant from bottom of the radiator and engine block [near oil filter for FWD]. Will take about 1/2 hr to drain out. [You can do a partial drain as well. Much simpler to drain all other wise you have to estimate how much to drain ... coolant level must drop below the intake level, else you will have coolant in the intake manifold.
4. Tape two strips of 3M and put it on the wind screen along the edge of wiper.
5. Remove the wiper arms by undoing the nuts that hold the wiper.
6. Remove the plastic hold down rivets and remove the two ventilator pieces. [plastic below the wiper arms]
7. Disconnect the wires for the wiper motor and remove bolts and lift off the wiper motor-arm assembly.
8. Remove bolts and lift out the outer cowl top panel [metal box].
9. Remove air filter and filter box [note two hoses that come to the box + hose and carefully unhook the acc cable].
10. Remove the acc cable. Loosen the lock nut and pull out the slug from the butterfly wheel.
11. Do the same with the cruise control throttle cable.
12. Remove the v-bank cover ("L" and 3 hex-key nuts)
13. Disconnect the maf connector. Loosen the phillips screw wire clamps of the air intake. Remove the air intake.
14. Mark and disconnect hoses attached to the throttle body [TB]. Disconnect the two electrical connectors. There are 3 nuts connecting the TB to air intake chamber and the fourth is near the firewall (hidden from plain view). One hose at the bottom can be loosened when the TB is removed.
15. Air-intake chamber [AIC] removal. Disconnect all the hoses (pre-mark) and connectors. Undo the nut holding ground wires on the passenger side of the AIC. Loosen the bolts holding the AIC to the engine block.
15 continued (b)... the hardest step is to loosen the 14mm hidden bolt. Locate the black metal hook [#1 engine hanger] near the firewall on the passenger side of [AIC]. You have to squeeze 14mm small socket and drive in there. The trick is to loosen it enough, while still allowing the socket to be removed. If the spin the bolt too much the head will stick out too far and you will not be able to remove the socket. Now you can struggle with finger to undo the rest or use a wrench [or thin gear head] to undo the rest. By loosing the bolt, the head will come out enough to clear the "U" of the engine hanger.
15 continued (c): Remove the bolt holding the PS pressure tube near firewall.
15 continued (d): Lift the [AIC] up and partially out. There is yet another ground cable at the back tied by a screw.

Cleanup time>> make sure your work environment is dust free and clean. Use the Shop vac to clean up the head area. In my case the harness box had crumbled. Vacuum and vacuum again.

16. Disconnect the fuel pressure line. Be careful as there may be a bit of fuel spill ... no open flame etc. In the engine bay way below the brake booster is the fuel quick connect. The cover is an upside down "U" shaped plastic. Squeeze the two sides and lift the cover off. Twist the pipe going towards the engine by half a turn and the pipe will separate. [as long as battery is disconnected and the key is removed the pump can not come on].

17. Start disconnecting the hoses and connectors to the intake manifold assembly [IMA]. Mark them. Note, some of the hoses may already be free from the far end.

18. Remove bolts of the top engine mount holding down the water outlet. Remove all bolts and the nuts on the studs. Note few bolts are short.

19. Before lifting off the IMA clean the area. Lift the IMA and with six clean rags stuff the intake holes ... anything that goes there will be impossible to extract.

20. Disconnect the connectors from the sensors. My clips broke and the harness had to be replaced. You will need 27mm open ended wrench or adjustable wrench. You can easily replace both sensors without removing the hose.

21. I had to struggle to release the harness from the driver side of the engine. The trick is to lift the lock towards the wire (away from the engine) and slide towards the cabin. I found it easier to attach the wires to the sensor and then thread the connector. Remember to snap on the harness stand-off as that will lift the wire of the hot surface.

Disassembly is complete.

Reassembly is much easier. Just reverse the steps and use new gaskets. There is a channel for coolant and if the gasket is worn/bad, you can get coolant in the intake. OEM gaskets are not soft/rubbery.

Dont forget the hidden bolts and ground wires.

Line up the wiper blades with the masking tape and toque down the holding nuts.

Tighten the coolant drain plugs. 1:1 mix ratio is not necessary {in fact a bit more water is preferred ... look at the mix ratio on the bottle**. Start by making a 1:1 mixture and top up with just water. Remember to add the mix in the overflow reservoir ... you dont want to top it with just water. It may take a day or two to have the system full or purged of air. Remember to run the heater too.


Safety Check: Check that the fuel connector does not leak.


Ref: Look up the DIY for coolant replacement and IACV cleanup thread.

Shortcuts: I was assured you need not remove the wiper motor/cowl. I needed to paint the faded plastic so I went ahead and removed it. I think the access is much easier and my hands are large .. so very well worth it.

Extras: My CEL only complained about one sensor, but I went ahead replaced both. Some suggest that the bypass hose should be replaced ... well mine looked in good shape and I decided not to touch it.
The wire carrier was in bits and pieces for me. Per-suggestions I have used high temp loom and suspended it by a bridge made out of coat hanger.

Torques:
IMA hold down 11ft-lb
AIC hold down 32 ft-lb
Engine mount long bolts 47 ft-lb
Engine mount short bolt 23 ft-lb
Wiper arm nut 18-lb-ft

Salim
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Last edited by salimshah; 03-03-10 at 10:10 AM..
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Old 03-03-10, 12:19 AM   #2
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Wiper motor assembly:
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Old 03-03-10, 12:22 AM   #3
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Cruise control and throttle cable
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Old 03-03-10, 12:31 AM   #4
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Throttle Body with two nuts visible at top edge. The third is hidden in the direction I am pointing. One more bolt is near the fire wall [the support is exposed in next picture]
Note: The black object on the top is part of the cowl/wiper-motor. It will not be there if you remove it earlier.
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Old 03-03-10, 12:35 AM   #5
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Throttle body removed and upside down. You can see my way of labelling. In the background you can see the coolant outlet and the top engine mount.
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Old 03-03-10, 12:41 AM   #6
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Wrench on the Air intake chamber hidden bolt (driver side). IN the foreground you can see the mounting bolt pass through hole for the hidden bolt of the throttle body.
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Old 03-03-10, 12:46 AM   #7
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Ground post and nut on the pass side on Air intake Chamber. Note there is another gnd post at the back of the AIC which you can easily get to once the AIC is lifted off [remember to secure the hidden gnd post before you secure the AIC].
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Old 03-03-10, 12:51 AM   #8
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Getting ready to tackle the hidden securing the AIC. You can faintly make out the black hook in the shadow of the 14mm socket. Remember to unthread it enough that the socket can be removed. If you can not remove the socket, thread some back in.
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Old 03-03-10, 12:57 AM   #9
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Gray (high temp) loom hanging off a bridge constructed out of a coat hanger. Note the loom and wires are supported above the block. Every thing is secure ... no rubbing/rattling and the wires are lifted of the hot engine head. I have a 1/4" torx socket on one of the studs.
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Old 03-03-10, 01:01 AM   #10
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Cowl wipers all buttoned up. The plastic is painted flat black. The reflection from light makes it lock blotchy, but in real life it is great.
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Old 03-03-10, 01:04 AM   #11
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Here we come full circle ... The end and where I started from.
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Old 03-03-10, 05:38 AM   #12
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I did mine in about 3.5hrs with the assistance of one of my trusted technicians working with me.
There are some of those steps you could bypass such as removal of the wipers but just that I didn't take any picture in the process.
Well done anyway.
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Old 03-03-10, 08:29 AM   #13
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Make sure to put the link to this DIY in the DIY link at the top of the forum.
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Homepage of my 1999 RX300 AWD
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Old 03-03-10, 08:55 AM   #14
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One of the things I did not do was acknowledge all the help/support from fellow members. So thank you all ... If I list the names I am sure I will miss some one.

My knock sensor code would come on and then stay off for a while. I did run 2 treatments of fuel injector cleaner but then eventually took advantage of a warm day in winter month.

As far as time is concerned, I did take it slow and spent time in labelling the hoses.

I would say removing and reassembling the cowl added 30-45minutes. If I was to guess it helped be gain 30min or more in working with the thing removed. [I needed to paint the plastic so, I had to take it off].

I did struggle with the hidden bolt of AIC [30 min on one bolt].

15 minutes just cleaning the debries.

Worst for me was separating the knock sensor wire harness 45min if not more. [I was too tired at that point].

Another 45minutes in jury rigging the injector-spark-wire harness.


Add the frequent breaks ... searching for tools which were right in front of me etc etc and the time just added up.

Net ... It can be done in shorter time, but reserve 6-8 hrs.

Salim
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Old 03-03-10, 12:56 PM   #15
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Very nice job Salimshah! I'm curious, what is your mileage? It appears these things go our at a wide range of ages.

I had about 108,000 on mine when the code popped, I dealt with it for several months before biting the bullet. I considered that pretty early!
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Old 03-03-10, 12:56 PM
 
 
 
 
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1999, arm, break, clean, cleaner, engine, fuel, knock, lexus, location, replace, rx300, sensor, sensors, shaking, wiper

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