Roach90

I know what the sensor does, but it is possible that it would run fine without the knock sensor plugged in?

background 1990 4x4 4r 3.0L auto (everything stock cept stereo)
New to board. i just blew a head gasket between the #4 and #6 and a water journal. I have checked with toyota and mine is not affected by the service campain. i have disassembled it and when i removed the lower intake, i found that the knock sensor was there but the wire was not. i have searched the wiring harnes by the injector connectors and couldnt find the cut wire.

now the question

where do i go from here? do i just run another wire from the sensor to the ECU? do i leave it the way it is?

Roach90

*bump*

i am starting the assembly tomorrow and need to know what i should do about the sensor.

thanks in advance

Noltz

I think you know the answer - fix it properly. The engine will run without the sensor in place. But without a knock sensor, the ECU will not pull back the timing if you start knocking. And the sensors can pick it up way before your ear can.

Looking at my diagram, I see your knock wire is Black, from Connector B, pin 5 at the ECU. I may be misreading it, but it appears the sensor wire is shielded - so it may not be part of the main wiring harness. There are other solid black wires from the ECU... be sure it's B5 you tap.

I'll try and have a look at mine in the morning, but with the intake as it is I don't know what I'll be able to see.

Noltz

And in case I'm not awake or forget to post, the B connector has 16 wires on it;

B1 - Grn/Blk - to the MAF and TPS
B2 - Yel/Red - to the MAF
B3 - Yel/Blk - to the MAF
B4 - Grn/Blu - to the Coolant Temp sensor
B5 - Blk - to the Knock sensor
B6 - Blk - to the Oxygen Sensor

Yoda

The knock sensor should have a separate short wire attached to it, It is about 8 inches long and it is recommended to replace that wire every time you are in there. It feeds out between the intake runners on the left side (drivers) and connects to a plug on the main engine harness.

Roach90

thanks guys, i wasnt sure what to do right now. so i just put new wire on the plug and ran it out the passageway between the head and intake. i wll continue searching for the correct wire going to the ECU. if i cant find it by the time it is all back together, then i will run a new one. i have plenty of shielded 16awg wire available.

the plug in the main harness is missing and it looks like the wire was removed from the harness as well.

thanks again for the quick responses!

Roach90

ok, i finally found out what happened to the knock sensor. evidently the original wire broke and instead of removing the intake to replace, they relocated it to the driver side head (right above the Exhaust manifold). I know it is a pain in the butt to have it under the intake, but i moved it to the correct position. so far everything is going back together smoothly for now. i am waiting on a new oil pump and pressure sending unit. i might as well do it all (timing belt, water pump, tensioners).

this is a bigger job than i thought it was going to be. on my last toyota, i build a 22r/20r hybrid and it ended up running like a raped ape. this motor is definitely not as easy to work on as the 22r or the 20r.

Thanks again for your help

a2thea7705

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Im missing the same plug. Any idea where to get one or a part number.
Thanks

Kiroshu

IT WILL MAKE IT RUN BETTER! Personal exp with em. My dads 1990 3.0 knock sensor went out and of couse the engine light came on and it was runnin richer than fresh dog sh#@t. Cause see it conduses the computer in it and makes it run terrible and hesitate badly. Get it fixed it costs alot but yea.