Knock Sensor Cable Snapped

[paul3944]

Hi All,

After a bit of advice.  Managed to snap the Knock sensor cable right at the point where it dissapears into the loom :mad:

Can I run a new wire straight from the sensor bypassing the loom and down into the ECU (PFC) or is it grounded somewhere in the loom.

Any help on this would be much appreciated, dont fancy stripping out the loom again.....

Regards,
Paul

[jon103a]

the loom is shielded and the sensor critical, any signal change due to resistance or interferance can cause problems. best fit a new sensor and carefully observe the tightning torque specification as it is critical, to loose and it will vibrate causing the car to see knock and to tight will damage the sensor- really should use torque wrench

[ro284]

Is this an FD Paul? i have a known good one, 40 inc P&P If it may help.
Bob

[jackaleks]

you\'re on a Power FC so i wouldn\'t bother with the knock sensor. it doesn\'t have an effect on fuelling/timing and it\'s innacurate and pointless anyway.

[SiH]

Yup, gonna ditch mine as it\'s boned

[trotter]

you\'re on a Power FC so i wouldn\'t bother with the knock sensor. it doesn\'t have an effect on fuelling/timing and it\'s innacurate and pointless anyway.

^^this, very much this

[jon103a]

you\'re on a Power FC so i wouldn\'t bother with the knock sensor. it doesn\'t have an effect on fuelling/timing and it\'s innacurate and pointless anyway.

curios as to who told you that?. jon.

[trotter]

the stock ECU uses the knock sensor to control ignition timing as per a normal car. ie - hit the block with a hammer and you\'ll hear the timing change.

The PFC however, doesn\'t have the facility to interpret the signal and make changes to the timing accordingly (it\'s mentioned in the manual IIRC). All it does is flash the \'HEAT\' light three times to show you are getting a knock reading of greater than a programmed value. The value itself doesn\'t mean anything anyway - it\'s just a nominal figure.

As for the sensor being crap, it\'s a common acceptance for RX-7\'s in general - the sensor is just a microphone placed next to the block which is \'tuned\' to hear certain frequencies that knock tends to display. The problem however is that other things can set it off too. In no particular order mine was set off by:

Exhaust
Dump valve
Road noise
Stereo a few times!!

Highest I ever seen mine read was something like 170 odds, spoke to Pip @ WGT who told me that if it was actual knock then the seals would have gone long ago. If you have a conservative map then you shouldn\'t see knock anyway so you can not worry about it - also helps to run on as high-octane fuel as you can get your hands on.

HTH

graeme

[jackaleks]

curios as to who told you that?. jon.

don\'t trust the stock knock sensor, I\'d rather poo in my hands and clap than rely on the readings, even new ones

 
but yeah, as trotter said it picks up literally every random bit of noise. mine jumps up to around 80 if i so much as look at a speed bump.

[jon103a]

ok, always good to know these cars little quirks, thanks. jon.

[paul3944]

Many thanks for the all info  I managed to cut open the loom and solder in a new wire. Will see if its any good.

Many thanks
Paul