2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

Knock sensor wire??

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Old Apr 22, 2009 | 07:04 PM
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Shpee
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Knock sensor wire??

ok on my 87 TII i think its the knock sensor( hexagon shaped sensor on the center iron below oil fill neck) is not hooked up to anything...Its just has one black wire, does it hurt to not have it hooked up?? Also where does the knock sensor wire run too?? does it run out of the same wire loom as the CAS?? cause i also have a single black wire thats not hooked up to anything there also

thanx
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Old Apr 22, 2009 | 07:58 PM
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If your knock sensor is not hooked up, the ecu will retard the timing alot to be safe.

On the S4, there is suppose to be a gray wire that goes from the knock sensor to the knock control unit. From reading the wiring diagram, it seems that there is a black wire that ties into the gray wire down the line somewhere. That same black wire also goes to the ecu, and the knock control unit. Seems like its a ground wire.

look in the fsm in the wiring section. You can also find the knock control unit in the Fuel Emissions Turbo section page 4B-52

is your oil pressure sending unit hooked up? That black wire is probably that wire.
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Old Apr 22, 2009 | 08:12 PM
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ya the oil pressure gauge is working fine....i just thought they might go to each other since there both in the same area and both single black wires...the one come out of the same loom as the CAS...
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Old Apr 22, 2009 | 08:18 PM
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Shpee
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sry correction the one wire comes out of the wire loom where where tps wires come out of not the CAS....sry
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Old Apr 23, 2009 | 06:00 PM
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anybody kno nething else about this?? does it affect nething to not have the knock sensor hooked up?
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Old Apr 23, 2009 | 06:14 PM
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Originally Posted by Black Knight RX7 FC3S
If your knock sensor is not hooked up, the ecu will retard the timing alot to be safe.

On the S4, there is suppose to be a gray wire that goes from the knock sensor to the knock control unit. From reading the wiring diagram, it seems that there is a black wire that ties into the gray wire down the line somewhere. That same black wire also goes to the ecu, and the knock control unit. Seems like its a ground wire.

look in the fsm in the wiring section. You can also find the knock control unit in the Fuel Emissions Turbo section page 4B-52

is your oil pressure sending unit hooked up? That black wire is probably that wire.
Not sure thats correct since the ECU looks for input from the sensor to retard timing and the max timing retard is not but a few degrees. Most knock sensors on most cars stopped working years ago, not too mention it takes a HELL of a knock to set that system off.
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Old Apr 23, 2009 | 07:03 PM
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The ECU won't retard timing if the knock sensor isn't hooked up. It will only retard time if it is hooked up and you start to get knock.

Mine isn't hooked up on my turbo swap, with no effect. Hailers and others suggest not bothering with them since your engine will likely be damaged by the time they work anyway. I tend to agree.
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Old Apr 23, 2009 | 09:08 PM
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Those knock sensors are highly sensitive to any sort of extra vibration. I log my stock knock sensor with my Power FC, and at the time I believe i had a loose motor mount because the readings were pretty erratic.
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Old Apr 23, 2009 | 09:38 PM
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I have an N/A harness in my car and never bothered to wire up the knock sensor.

it isn't that important.
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Old Apr 23, 2009 | 09:41 PM
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well i guess thats prob y it wasnt hooked up,,,i wont bother with it either

thanx for all the replies!!
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