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Registered
Join Date: Jun 2008
Location: Paris, France
Posts: 101
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Where is the knock sensor 2 on a 993 carrera?
Hello,
i have an error code from the DME reading knock sensor 2 on my '96 993 carrera. I guess it's the sensor itself, because a bad fuel would have trigger both sensors from each cylinders banks. The engine rattles at idle. I never changed one of those sensors and wonder were are they located, and how can i easily get to the bank 2 sensor? i guess i will have to remove the air filter assembly, and maybe the air intake distributor? any idea? let me know thanks Cedric |
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05-30-2010, 10:23 AM
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Join Date: Jan 2005
Location: north america
Posts: 2,228
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If the sensor is faulty you might be able to reach them by removing the cooling fan assembly . The sensors sit in the middle of each cylinder bank, on the top side of the cylinder.
if you look at the engine shroud in the area around the base of the manifold intake pipes, you will see a black wire that goes through the engine shroud, thats roughly where they are. Your problem might be only a loose connection at the plug, you may also be able to test them for resistance to see if they are in spec at the plug, not sure though. Good luck |
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05-30-2010, 02:43 PM
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Join Date: Jul 2001
Location: Portland Oregon
Posts: 7,007
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Quote:
Knock sensor failure is pretty rare and I'd suggest investigating the cause of the engine rattle. Beyond confirming the integrity of the electrical connector and the sensors themselves, I would check the distributor drive belt. After that, the judicious use of a stethoscope will help you.
__________________
Steve Weiner Rennsport Systems Portland Oregon (503) 244-0990 porsche@rennsportsystems.com www.rennsportsystems.com Last edited by Steve@Rennsport; 05-30-2010 at 11:47 PM.. |
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05-30-2010, 11:45 PM
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Join Date: Jun 2008
Location: Paris, France
Posts: 101
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i really don't think that the distributor drive belt is the problem, because the car runs overall very good, but just rattles when hot.
Furthermore, if the engine would work on only 6 spark plugs, i would have a bunch of error codes coming out, and i would notice it when i drive. I work with the PST2, and the error code "knock sensor 2" keeps coming back each time i clear the memory. The sensor itself shows wrong values (voltage, resistance, ect), so i'm pretty confident that the problem is here. The problem, is that changing this sensor seems to be a pita. I would have to remove all belts, the fan assembly with the alternator...and i'm not even sure to have enough space under the engine shroud to access the sensors. I guess i will have to replace it first and see what happens next; i don't feel like tearing the car apart twice |
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05-31-2010, 03:45 AM
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The factory manual diagram shows the knock sensors under the head bolt torquing page section
as having a location on top of cylinders 2 and 5. See enclosed photo. Good luck as you may have to disassemble the entire top manifold to get at replacing them. 
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05-31-2010, 04:44 AM
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I think Steve's suggestions are quite reasonable since the rattling is the reason why your knock sensors are picking up "knocking". So that says the sensors are functioning in their intended application. I assume sensor 2 is covering the cylinders 4-6 bank (passenger side, right side) Listen for the rattle on that side of the engine. When you fix the source of the rattle will likely stop the error code for knocking from reappearing.
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05-31-2010, 04:50 AM
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