Knock Sensor Recommendations?

[jldyer]

Hi all...Does anyone have a suggestion which brand knock sensor would be the best for my 1993 J30t? I see cheap prices and expensive prices

Also, has anyone else noticed that when you replace one sensor, another goes bad (or maybe it was bad all along, but masked because another sensor was bad)? I replaced the MAF, both oxygen sensors, coolant temp sensor, and now the knock sensor seems to be bad (power is gone, accelaration is bad, fuel economy dropped from 20mpg to 16mpg). I hate to even guess what could be next.

Jldyer

[yodawill2000]

Have you checked the codes to make sure its the KS ?
Look for a 300ZX knock sensor.
They seem to go cheaper but the are the same as ours.

[Talamascan]

Before you buy another KS, try this: If the ECU has indeed thrown a KS code, try disconnecting the battary for an hour and see if that clears the code. When I was trouble shooting my KS sensor, that was the only way I was able to snap my ECU out of the super rich safety map it switched too every time I tripped the circuit.

Obviously, if you reconnect the battary and the ECU throws yet another KS code, then you either need a new KS, or (more likely) you need a new harness. Z1 Motorsport sells both.

[jldyer]

@yodawill2000 -- I haven't checked for any codes. I'll have to do that. This all started when I replaced the coolant temp sensor. The plug (harness) was cracked, so I cut the old one off and added the new plug and a new sensor. Is it possible the car would run and fuses wouldn't blow if I connected the two wires backwards?

@Talamascan -- How long do you have to drive the car after you disconnect the battery for an hour before everything sets properly?

Jeff

[J30tChumpCar]

I believe the coolant sensor is a thermistor, polarity shouldnt matter, culd be wrong but either way it has nothing to do with the knock sensor which polarity does matter.

It is very common to find the plug and one terminal on the KS corroded green, a simple fix is to buy a new sensor and short harness then relocate on top of the intake manifold, as the original is buried UNDER the lower intake manifold, there is a writeup somewhere...

[fourdrinie]

where-is-j30-knock-sensor-cable-ecu-sid ... 82494.html

[Talamascan]

The change-over should be instant upon restart. Whenever I tripped my KS circuit, the car basically ran like crap; down an easy 30 hp, high idle and general sluggish behavior. Then I would reconnect the circuit and disconnect the battary for an hour, and upon reconnection the car would start and run good as new every time.

I suspect that you could shorten the disconnection period, but I simply adopted 1 hour because that's what is recommended for my son's Civic when we add significant performance modifications.

[jldyer]

Ok...so why would I get such a huge drop in fuel economy and sluggish performance when I changed my coolant temp sensor?

[Talamascan]

Without checking the ecu for codes, it's pretty difficult to say at this point.

[jldyer]

55...which, if I remember correctly, is "NO error codes" found.

[jldyer]

So...I'm not getting any error codes...does anyone have any ideas what would be causing my significant drop in mpg and power when warm?

[Talamascan]

I know this sounds really basic, but it works.

Check your tail pipe. If it's got dry black soot on it, then it's definately running rich and you need to continue checking off any other possible causes of a rich condition that you have not already looked at. For example, if you live in a cold climate with a lot of short distance driving, a thermostat that is stuck wide open can cause a rich condition and escape detection.

If it's got oily black soot on it, then perform a compression test.

If the tail pipe is clean, then I'd start looking at intake, exhaust or fuel filter restrictions.

[jldyer]

Dry black soot. where do the wires for the coolant temp sensor come from?

[fourdrinie]

according to the FSM which you should download, the two connections from the engine coolant temp sensor go back to the ECM (Engine Control Module)
The Y/G wire goes back to pin 59
The OR/L wire goes back to pin 43 which is a ground pin.
Doesnt look like it would make much difference if connections were transposed as its just a thermistor as J30TChumpcar refers

[yodawill2000]

If it started when the temp sensor was replaced...
Maybe a defective sensor ??
If it was showing cold when the engine is warm, All sorts of settings would be borked.

[fourdrinie]

agree with Yodawill 2000..a defective sensor would cause all sorts of issues..but would throw a PO125 code..


check resistance across the two terminals, which placing the sensor in hot water with a thermometer:

water temp: 68 deg - resistance 2.1-2.9 K-ohms
water temp: 122 deg - resistance 0.68-1.0 K-ohms
water temp: 194 deg - resistance .236-.260 K-ohms