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Discussion Starter #1
OK here goes the story of my 2000 VW Bora 115 Tdi. Around 8 months ago it started going into limp mode on occassion, just like all the other cases, under high load. A swift flick of the ignition would cure the problem. Then 2-3 months ago it went into permanent limp mode.

Having hooked up the car to the VAG COM it reports the following fault codes:

17964 - Charge Pressure Control: Negative Deviation P1556 - 35-10 - - - Intermittent 17552 - Engine Speed Sensor (G28): Implausible Signal P0321 - 35-10 - - - Intermittent

I’ve had the following work done to the car:

1.It’s on its 3rd MAF. I’m fairly confident the MAF(s) is good. Putting it on another car it works just fine according to VAG COM.
2.The turbo has been stripped and the mechanic tells me the Vanes are moving fine.
3.New N75 valve.


Here’s the output from VAG come of the MAF and intake pressure:






Finally another strange thing happens when reaching a high rpm
http://www.youtube.com/watch?v=jJkVpVpikZQ
Strangely it also switches the traction control light on and it stays on until the ignition is reset.

Unless anyone can suggest otherwise am I best starting looking at the acuator to see if it is able to move the rod? Given I have the VAG COM can I use this to test it an see it move? Is it best to try and look at it from underneath or top?

Thanks for your help
Carl
 

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It sounds like the engine is cutting out. Possible causes is fueling, electrical, or air. Once common cause is faulty vacuum lines. A single crack can cause malfunction. See here for some more troubleshooting tips:
http://www.myturbodiesel.com/1000q_how_to/multi/limpmodetdi.htm Yours is also low power since it seems to have gone into permanent limp mode.

Do a boost leak test. It's possible there's a leak which is getting worse. This is just a guess. http://www.myturbodiesel.com/1000q_how_to/multi/boostleaks.htm

The speed sensor code is the speed sensor or wiring. See here for more details: http://wiki.ross-tech.com/index.php/16705/P0321/000801

The charge pressure code - first do a boost leak test. Also test the VNT mechanism - see here for more details: http://www.myturbodiesel.com/1000q_how_to/a4/VNTadjust.htm

No clue why the traction control light is on.
 

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Are you sure all the vac lines are correct and not cracked? If the traction control light is on the traction control system must have an error not related to limp mode.
 

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The TC light will come on if there is a break in the elec current, as though the ignition is switched off, sounds like you may have an elec fault causing your problems
 

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After my orginal post I have done nothing to the car except disable the egr. A few weeks later I noticed that my permanent limp mode went to occasional limp mode requiring me to restart the ignition to get the power back. However this weekend I drove 200 miles perfectly. Not sure if disabling the egr was just conincidental?
 

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ABS Sensors?

Awesome video!

I'm inclined to look more at the traction control system for faults.

Check your ABS sensors in VCDS. I don't remember which channel, but you can get readings for all 4 wheels. Ensure these are all exactly the same, especially at speed.

Second, check the ABS rings, the metal ring with the holes in it that sits just behind the hub and just millimeters from the ABS sensor. If that is rusted, corroded, has gunk in a hole or is hitting (!) the ABS sensor the engine will cut out like that.
 

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Discussion Starter #9
Thanks - Also regarding testing the N75. I do have VAG come and know how to run the output test. However when it passes through the N75 test what should I look for?

Rumours suggest I should be able to hear the N75 click? Should it also exercise the actuator i.e. I should be able to see it moving?

Thanks again,
Carl
 

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Split vacuum hose connected to the N75 valve. Patched it with duct tape...all power back. A year and it was staring me in the face on the bulkhead...is swearing allowed on here?







Yes I'll get the vacuum hose replaced on Saturday.
 
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