So I followed this -

 

http://www.zhome.com/ZCMnL/PICS/detonationSensor/detonationSensor.html

 

I tested the sensor side of the connector and my meter showed '1', which was the default display on my meter when selecting the ohm settings. There was no movement, nothing, as if I wasn't testing anything. Doing the same ECU side of the connector, I was getting 560 Ohm, which I believe is ok, what I should be getting.

 

Then I stuck a 1k resistor in the ECU side of my connector, I started her up and lo and behold she ran far better, revved without stumbling or miss-firing, super smooth compared to before! However below 1000rpm wasn't good, without providing gas the engine finally would cut out, but I think this is a separate issue as I had been playing with the TPS a few weeks back, so I think the idle needs sorting but otherwise the knock sensor has obviously been at the route of the problem.

 

The thing is using the resistor I'm still getting code 34!

 

The resistor was only pushed into the connector, but had a good connection. Testing it with the meter the resistor actually shows 980 Ohm, not 1k, but would 20 Ohm make the ECU flag a code 34?

 

If the wiring to the ECU was broken, then the resistor wouldn't have done anything, so everything suggests that my knock sensor (or its harness) is dodgy.

 

So, I think I do need to replace my knock sensor, but not convinced it will clear my code.

It's likely shorting on the main harness. That's what mine was doing, pain to repair as it's a screened cable and access is crap.

Why not fit the resistor next to the ECU and just remove the damaged harness out of the equation?

 

Then I stuck a 1k resistor in the ECU side of my connector, I started her up and lo and behold she ran far better, revved without stumbling or miss-firing, super smooth compared to before!

 

 

However below 1000rpm wasn't good, without providing gas the engine finally would cut out, but I think this is a separate issue as I had been playing with the TPS a few weeks back, so I think the idle needs sorting but otherwise the knock sensor has obviously been at the route of the problem.

 

The thing is using the resistor I'm still getting code 34!

 

 

 

Ok a few classic misunderstanding there buddy, dont feel bad very common, firstly unless you have a very low impedance tester that can generate a high spike oputput such as a megga meter you will not read anything off the actual knock sensor as the reading is off the scale.

 

 

The resister you mention a 1k ohm is the wrong one, what you want is a 1 meg ohm, that is why you are still getting the code 34 reading as the ecu still sees a problem.

 

 

So back to the running issue, even if you had the correct resister in it would not of corrected any running issue at tickover as it has no bearing on how the engine runs then, its primary purpose is to reduce the chance of damage when knock is detected on load and only in a small rev range whilst on boost, it then reduces the available boost via the boost solenoids and retards the ignition, both of which will reign in the knock and save damage to the engine, when that occurs the car will run fine but in safety mode and reduced power until switched off and on again.

 

Some years back we did a little straw poll of cars coming into the workshop and was amazed to find as high as 70% came in for general service work had the precondition of a failed knock circuit often without the owner even knowing. So what ever running issue you have it will not be the failed knock sensor circuit, you mentioned there seemed some improvement, well as we now know the resister was the wrong one and the code 34 is still present that sort of suggests you either just feel it seemed better or maybe and more likely moving the loom around has improved a connection somewhere, like to an injector or earth tag maybe.

 

So get a 1 meg ohm resister ( see pic below for band colours ) and fit it to the ecu side of the connector, then after restting any codes run the engine and retest, if the code is gone great, if not then likely the cable to the ecu has an issue and will need fitting at the ecu connector.

 

Once this is resolved you can look at the running issue, check timing, afm voltage on ConZult or similar, TPS settings and air leaks, even dirty throttle body butterflies can cause poor running, and don`t forget to check battery connection, these can become high resistance\and cause all sorts of odd issues as well as checking for a good charge from the alternator.

 

One word of caution, removing the knock sensor has to be considered a work around to the problem, but that said, if your engine is set up correctly and using good fuel you will have no issue with it and there are many, many zeds running around in just this manner mine included, and as long as you understand what is happening that is fine.

 

 

Jeff

 

 

Why not fit the resistor next to the ECU and just remove the damaged harness out of the equation?

 

Cheers, I pondered this, but didn't have time today, it made sense to eliminate the harness being the issue, but wanted to check here first too. :)

 

The resister you mention a 1k ohm is the wrong one, what you want is a 1 meg ohm, that is why you are still getting the code 34 reading as the ecu still sees a problem.

 

[ATTACH=CONFIG]106809[/ATTACH]

 

Thanks for the advice, it all makes sense, didn't even consider I was using an incorrect resister - this is it -

 

 

I'll get the correct resister and try again, but there definitely was an improvement in engine running, before it was a mess of spluttering, missing, stumbling, today it was actually smooth above 1000rpm.

 

However, from what you're saying, if so many Zeds are running without a functioning knock sensor, I'm tempted to do that. Although I plan to replace the plenum and clean out the IACV, do the coolant bypass, and replace vacuum pipes with silicone tubing, so as I'm going that far...

1M Ohm resister ordered! :)

I would personally replace the broken loom section and refit a new sensor if you are taking off the plenum.

I would replace the sensor and fit new wiring loom to it and then run the wiring to the ECU and connect it where the resistor is.

For the minute you could use the resistor as a bypass / temporary fix??

Only an idea.... lol

So, today I finally got around to inserting the 1M Ohm resister, and all was fine, still have a bit of an idle issue, but after playing with the TPS I actually had her idling at around 700rpm, at least temporally. when I pulled the codes I got good old 55!

 

So clearly I have a dodgy knock sensor or harness.

 

I'll be pulling off the plenum, changing that over, and someone mentioned that you can replace the knock sensor without removing the lower intake manifold. Can someone please tell me how easy is this? What I mean is am I going to waste half a day trying to remove the knock sensor with the lower intake in place, so may as well spend the time removing it anyway?

You should not be "playing" with the TPS to adjust the idle...the TPS is called a "throttle position sensor" for a reason and needs to be at a certain position (so it outputs around 0.45 Volt)

There is a idle adjustment screw at the back of the engine and this should be used to adjust the idle.

 

replacing the knock sensor with the engine in the car is quite a bit of work and not a beginners job.

Not sure how one can replace the knock sensor without removing the lower intake (and EGR-valve), as there is no way you can reach it without removing these.

 

Easier option would be a relocation, although not the ideal option, but better then no or a bypassed sensor

forgot the link: http://twinturbo.net/nissan/300zx/forums/technical/view/786419/TECH-Detonation-Sensor-Relocation.html

I would personally replace the broken loom section and refit a new sensor if you are taking off the plenum.

I would replace the sensor and fit new wiring loom to it and then run the wiring to the ECU and connect it where the resistor is.

For the minute you could use the resistor as a bypass / temporary fix??

Only an idea.... lol

 

Agreed, it's not worth the risk running these motors (or any other for that matter) with detonation, It can only end in tears.

You should not be "playing" with the TPS to adjust the idle...the TPS is called a "throttle position sensor" for a reason and needs to be at a certain position (so it outputs around 0.45 Volt)

There is a idle adjustment screw at the back of the engine and this should be used to adjust the idle.

 

replacing the knock sensor with the engine in the car is quite a bit of work and not a beginners job.

Not sure how one can replace the knock sensor without removing the lower intake (and EGR-valve), as there is no way you can reach it without removing these.

 

Easier option would be a relocation, although not the ideal option, but better then no or a bypassed sensor

 

I removed the EGR when I had the engine out. I was only 'playing' with the TPS to improve the idle, but I know it needs setting up correctly, but as I'll be pulling the plenum and cleaning out the IACV, I figured it didn't really matter at this stage.

 

I think it was in a different thread I was told you get get to the knock sensor without removing the lower intake, if the EGR was vacant.

 

Now that I'm seeing this image, it might just be possible! -

 

ok, looks like there's a range of knock sensors...ranging from about £50 to £150, should I be buying a dealer part perhaps? Quite a difference in price...