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'89 944S2
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Knock sensor wiring: shielded?
Hi all,
As I slowly grind towards repairing the bad idle in my S2, I have discovered a number of wires with what seems to be "Mouse damage". Of most concern is the wiring to the forward knock sensor. The wiring seems tone shielded. Can anyone confirm? Best method for repair in situ? Simply cover with heat shrink? Cheers and thanks Greg |
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04-19-2013, 11:56 PM
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Eric
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The braided shielding needs to be continuous from the knock sensor to its connection at the DME as it acts as the ground. If it is not, the knock sensor will not work and the DME will retard timing.
It would be difficult to get heat shrink over the wire without disconnecting it from the harness. You can use conductive foil tape though. To do this properly you will need to remove the intake manifold.
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Eric |
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04-20-2013, 12:02 AM
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'89 944S2
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Hi Erik,
The manifold is already off. Some one has suggested foil and electrical tape. Greg |
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04-20-2013, 12:39 AM
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Frankly my dear....
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Foil and electrical tape will not be a robust enough repair in an engine bay. I am guessing the suggestion is simply wrapping the wire with the foil and then covering it all with tape...?
A better solution would be to make sure a good electrical connection is made between the damaged ends of the braiding by soldering a 'jumper lead' across. This will ensure the sensor doesnt go open circuit at some point. Heat shrink over the repair is also a much better idea to finish, or use self-amalgamating rubber tape...not standard electrical PVC tape. The old foil and tape trick works with microphone and aerial co-ax cable repairs to a degree, however it cant hack it in an engine bay due to the heat, vibration, oil, water, etc. 
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Porsche - accept no substitute Blue 1999 Boxster - Brief encounter! Black 1988 944S - Ongoing project Black 1987 944S - Gone but not forgotten Metallic Black 1980 924 - Those were the days.... Red 1979 924 - Hmm Minerva blue 1979 924 - Where it all began! |
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04-20-2013, 01:32 PM
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'89 944S2
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Hi there,
Rhett, I cut back the insulation to ensure I found good braid either side of the brake. The break n the braid is not all the way around, say approx 50% gone. Strangely, or maybe not, the braid is not continuous to the OEM plug, rather it finishes approx <1" from the plug. I cannot get heat shrink over the plug so that is not an option. Bloody mice, I have just found extensive damage to the air on/heater/fan wiring. Grrrrr Greg |
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04-20-2013, 08:54 PM
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Frankly my dear....
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Hi Greg, just had a look at the wiring diagram, see below:
 Yep, it shows that on this sensor the braid is not the ground return, but is a grounded shield (to stop electrical interference, etc). So, as the braid is still OK 50% and it doesnt have to be a return you can simply wrap a piece of braid from a good piece of co-ax cable around the damage (this is better than foil) and then use rubber self-amalgamating tape as heat shrink wont fit. That should do it. 
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Porsche - accept no substitute Blue 1999 Boxster - Brief encounter! Black 1988 944S - Ongoing project Black 1987 944S - Gone but not forgotten Metallic Black 1980 924 - Those were the days.... Red 1979 924 - Hmm Minerva blue 1979 924 - Where it all began! |
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04-21-2013, 12:38 PM
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