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Discussion Starter #1
Or engine speed sensor if you prefer.
My 06 4.2 v8 with 156000 miles has been showing some symptoms of crankshaft position sensor failure the last month. (rough idling, sluggish acceleration, intermittent no start etc)
I am fairly new as her owner and have recently been chasing multiple vacuum leaks, completed the sparks plugs, new pcv valve, new battery and 2 new mass air flow sensors Among some other basic maintenance like the oil and air filters being changed.
It has also recently had both fuel pumps replaced (if one fails i figured while I'm in there go for gold) along side the fuel filter and the pressure regulator. For the fuel system all the parts used were VDO and seem to be working perfectly.
I was honestly hoping the other issues would rectify the on going issues with the idle, acceleration and the feeling that she was about to stall out.
The symptoms seemed to disappear for around week or so after all the repairs were completed, until the vacuum codes came back but along side them a new code.
16706- Engine speed sensor no signal

My question is has anyone had luck with replacing the actual sensor itself over this code especially if the vehicle is still starting? or have you found the true issue was in the wiring?
I have ordered a new sensor that includes the pigtail and will hopefully be installing Friday, but am concerned it may be a deeper issue?

She finally stalled out at a stop light today and is currently sitting in a parking lot waiting to get back to the garage.
like I said there is still something acting up in the vacuum lines but it is a relatively minor leak after replacing several hoses and the IMT actuator recently as well.


Also in regards to battery replacement has anyone ever had to flash the ECU because of the battery replacement? just curious if that could be causing some issues as well.
I got the vehicle for an amazing deal and love it dearly so I am doing my best at taking care of her, but she isn't making it easy on me...
Any and all suggestions welcome.
 

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2005 Touareg - 3.2L BMX
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Doubt it is a speed sensor error causing the poor performance. If the speed sensor fails car won’t start and will stop running if running. Could be camshaft sensors. Similar to speed sensor (halls magnet) but magnets used to determine camshaft position. The ecu uses the sensors for starting and timing. If camshaft sensors have issues will cause hard starting.

Would also make sure the all the fuel pump items replaced are operating properly. Could cause the poor performance. Car needs both pumps to operate. One pump behind driver is used at priming when you start car, after about 30 seconds the car runs off the pump behind passenger side. The fuel tank is kind of U shape with a pump in the primary larger side of tank and secondary pump in the smaller part of tank. The pump behind drivers side also transfers fuel from the larger side of tank to the smaller tank. A Rube Goldberg design.

Never had to flash ECU after battery change. Whenever the car loses battery power you get all kinds of errors when battery replaced or recharged. After a few starts the errors go away.
 

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I replaced the sensor on my v8 when it developed starting issues during short trips. i.e. it won’t start when the engine is at operating temperature. A new sensor fixed the problem.
 

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Discussion Starter #5
replacing the sensor tomorrow, with pigtail in case its the wiring giving me issues. fingers crossed it rectifies the issues!
I would think Cams would throw a code??
also found and repaired the final vacuum leak so hopefully she is back to prime here soon
 

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Yes generally the camshaft sensors may throw a code, but it is not unusual for the sensor preventing the car to start or long crank when hot and you don’t get a code. My car would start fine drive around a little stop, get back in car and would not start. Let the car sit a bit and would crank no problem. One of the sensors electronics failed when hot. It is not an uncommon problem with sensors. I have a VR6 engine not V8, however VW literature is clear that even an intermittent signal from the speed sensor will stop the car even if running. If you have an intermittent start issue could be a faulty speed sensor that when hot prevents starting. Don’t see how replacing the sensor will fix poor acceleration and rough idling.
 

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Take back last sentence. The position of the crankshaft relative to camshafts are determined by the speed sensor and the ecu uses the signal from the speed sensor to determine injection quantity and start of injection. So long story short could cause performance issues if working marginally. Stand by if the ecu gets no signal from speed sensor engine is switched off.
 

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replacing the sensor tomorrow, with pigtail in case its the wiring giving me issues. fingers crossed it rectifies the issues!
I would think Cams would throw a code??
also found and repaired the final vacuum leak so hopefully she is back to prime here soon
Did speed sensor correct problem?
 
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