Car Knock Sensor Issues

[SargeRX8]

My car was fine a of yesterday afternoon. I went to work then started it up after that. Car read 100 knock on startup. I reset my power fc max values and now my knock sensor will not read 1 or 0. It sits on 3 to 4 and tiny idle revs will raise it to 10. It is always hearing something. This is bad as I can no longer use this reliably.

Everytime my car starts it gets 70+ knock. It hasn't done this in a very long time, since my fuel pump failed.

Any ideas? Its an rb25det unopened.

[SargeRX8]

It done it when spark and fuel were removed too.

[Bsa]

Maybe one may have snapped and is sitting on the metal prong and causing it to read wrong

[SargeRX8]

Can I unplug one at a time and see if one is giving the problem? Are they reachable with the engine in the car?

[BOOZTJUNKEY]

I can reach both mine on the 32 it's tight but u can do it u should be able too mate it's preety common for them clips to become brittle and brake

[R.3.2.G.T.R]

loose starter motor?

[SargeRX8]

Ill be tightening anything I feel is loose, including the knock sensors. Apparently they should read 4v so ill test them too. They are picking up CONSTANT noise. No more sitting at 0 or 1, they are always on at least 3 when just idling and jittering up and down when touching the throttle.

[89CAL]

70+ on startup would indicate something to do with the starter motor. while the car is running there may be some vibrations through the starter causing knock readings. i know i get the most knock on startup sometimes. Its not so bad when i stop cranking before the engine has fully started so the starter motor isnt being over-run by the engine before disengaging the ring gear

I know my starter is on the car tight so its either a bit funny internally or maybe the thin plate on the bellhousing is vibrating with the starter motor

[SargeRX8]

My starter motor is fairly tight on there. I just pulled out the first knock sensor, its still reading the constant values. There is no way in hell I can reach the second one at the back of the motor so I am going to check the pinout on the ECU and measure the voltage of both of them. There is nothing I could have done to cause this which is why its annoying me.

Yesterday I got it to read 90 knock with the fuel and spark disabled from the fuel pump and from the coil packs. Today I disabled everything my removing the CAS wire, and it wouldn't knock no matter how long I cranked it. I plugged it back in and on the first engine turn, before it started spluttering or coughing, it read 100knock. I hope there isn't something wrong... If I could reach that rear knock sensor it would be sweet because then I can pinpoint the fault at the rear knock sensor or noise coming from the rear of the block.

[SargeRX8]

I just accidentally, and probably subconsciously intentionally, ripped out the wire from the rear knock sensor. No more funny readings. No more high knock readings, no more constant readings.... And now no more knock sensor watching the back 3 cylinders... f**k. That clip is f**king impossible to get to. I'm going to buy a second hand sensor and try get the old one out and a new one in.

Edit: f**k AGAIN. It just read 60 knock on f**king startup. The knock sensor must be too far from the rear of the motor to pick up that other noise the rear one was picking up. Now I f**ked my rear sensor for nothing. FUUUUUUUUUUUUUUUUUUUCK

Edited November 17, 2011 by SargeRX8

[89CAL]

Can you try another CAS? I just replaced my CAS because the bearing was on the way out and making alot of noise. Have had alot less knock since then, but my base timing is the same as it was with the old CAS

try and borrow one and see if it helps. If your knock reading goes down then you might need a new CAS.

If you havent touched your tune then it sounds a bit like something has partially failed. Just suggesting CAS, cause mine was very intemitetly throwing out high readings which werent really repeatable

[SargeRX8]

I have not changed anything in relation to the tune since this started. I installed my wideband sensor into the stock location, replacing the old narrowband and that was it. I do feel my CAS may be failing due to starting issues but do not have a spare to test it. The noise is being detected from the rear so I am leaning towards gearbox or starter noise. I don't get false readings when driving, only the startup knock and like the hummmmmmm which reads 3+ knock all the time(which now isn't a problem since I snapped that wire lol).

[DVS JEZ]

Most read a bit of noise when idling and revving. I wouldnt be too concerned with it. Throw it on the dyno and finish the tune by listening and without relying on the power fc knock reading so u know its right.