Resident TDi expert?? I have a question..

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toomanytoys
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Resident TDi expert?? I have a question..

Post by toomanytoys »

Not an alternative engine swap.. but calling on the TDi knowledge base for a poss solution.
Bro's Passat 2L TDi 170 keeps throwing EGR faults and going into safe mode...
Where is it located? Can I clean it/byass it? or is it a replace job?

Cheers

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Re: Resident TDi expert?? I have a question..

Post by ewenmaclean »

Hello,

it's pretty rare for the EGR code to throw the car into limp mode unless it's stuck open rather than stuck closed - there are various torque limits on limp mode, and I'm not that familar with PD engines. Many people blank off the EGR as it keeps the intake cooler and cleaner - it's an emissions thing which might save you a couple of mpg (debatable), but it definitely causes a lot of gunk in the intake manifold by mixing sooty exhaust gasses with oil spray from the CCV.

I would first try and clean it up as well as have a look at the intake manifold. It will a bendy type pipe between the exhaust manifold and inlet manifold bypassing the turbo and intercooler. It'll have a vacuum supply to it - you probably also have an anti-shudder valve (like a butterfly valve post intercooler) - which is probably nearby - don't confuse it with that! You can essentially bypass it just by blanking off the vacuum supply to it, or block it off more resolutely with a blanking plate. On mine I put two blanking plates and removed it completely as it freed up some space, but that was a non-pd AFN(ish) engine.

The problem with the error codes is that if you do blank it the MAP sensor will notice that no boost drop has been noticed when the EGR is supposedly passing exhaust gasses - you can actually change what the EGR expects in vag-com and so you might not get the error codes - search for EGR here and it'll tell you how to do it:

http://www.ross-tech.com/vag-com/cars/tdi.html" onclick="window.open(this.href);return false;

that adaptation worked well for me - never had an EGR fault after doing that, although when I did previously, I never got into limp mode. Limp mode is much more common from a problem with the N75 valve not N18 (EGR) valve, and a vacuum leak to the VNT actuator. On a VNT engine those two solenoid valves look almost identical. However - If the EGR valve was stuck open you'd definitely be getting problems - not so much if it were stuck closed. Any chance you could put the actual codes up?

Ewen
Last edited by ewenmaclean on 05 Jun 2013, 10:24, edited 2 times in total.

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ewenmaclean
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Re: Resident TDi expert?? I have a question..

Post by ewenmaclean »

by the way - here is a pic of what you're looking for I think:

Image

The silver tube on the right comes through a cooler from the exhaust manifold - the part on the left the other side of the induction tract is the actuator for the EGR.

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Re: Resident TDi expert?? I have a question..

Post by toomanytoys »

Cheers Ewen
Cant see the pic at the mo..
When I go over my bro's I will see what I can sort..
Don't have vag com.. so that might be an issue..
He got a mate to read the code with a universal reader.. and apparently the manual says if the light comes on its most likely the egr.. so we shall start there...

Thanks again.. :ok

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Re: Resident TDi expert?? I have a question..

Post by ewenmaclean »

sorry - website went down - hopefully that pic will be available again soon, so you can see what the EGR looks like on a PD170. Would certainly be helpful to know the code!

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Re: Resident TDi expert?? I have a question..

Post by Mr Soft »

On some VAG engines the throttle valve can also throw up the EGR fault, this then feels like limp mode, but it the case of the wifes car the nylon segment gear had worn, thus it didn't operate correctly, giving very little power.

Bob
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Re: Resident TDi expert?? I have a question..

Post by toomanytoys »

Ok.. cheers
Yep.. looks just like that.. I kinda worked out that it might be the EGR from the stainless pipe.. but wondered if it was on the other end..

Will check throttle too then...

Presume brake cleaner etc is best to shift the crud??? (after removing) :ok :ok

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Re: Resident TDi expert?? I have a question..

Post by lloydy »

Mr muscle worked the best on mine
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Re: Resident TDi expert?? I have a question..

Post by ewenmaclean »

Yeah - brake cleaner recommended or Mr Muscle as Lloyd says - can't think of much he hasn't done so that's a good tip ;-)

Sorry to be a pedant but a tdi technically doesn't have a throttle. That's why diesels need vacuum pumps. If you're referring to the anti-shudder valve then it functions as a binary throttle - completely free when running and blocked with ignition off - designed to prevent runaway. Worth checking its operation while you're there for sure though.

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Re: Resident TDi expert?? I have a question..

Post by max and caddy »

That valve on the front there is not normally a problem...but check its plug is not full of oil..the cooler on the back of the engine causes problems and may be blocked, or have a problem with the change over valve on it...after fixing the issue there is a software adjustment available to prevent future carbon build ups.

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Re: Resident TDi expert?? I have a question..

Post by toomanytoys »

so dismantle that and check and clean.. then check whatever is on the other end of the stainless pipe round to the manifold??

:ok

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Re: Resident TDi expert?? I have a question..

Post by mazz »

If your bros passat is 2007> EGR will throw car into limp mode. Two things fail here, ether electronic unit is u/s or flap had broke off inside valve, pretty common fault on the 2.0pd
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toomanytoys
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Re: Resident TDi expert?? I have a question..

Post by toomanytoys »

Cheers :ok
Have to go look at it yet.. :oops:
He's so peed off with the car that its on SORN at mo.... :rofl

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Re: Resident TDi expert?? I have a question..

Post by max and caddy »

Check the cooler on the back of the block, the roller fails on the actuator, the vac diaphragms split, the flap inside them sticks, or the electronic motor part fails, or they block up...or all 5 at once...full on pain to get off as well..

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Re: Resident TDi expert?? I have a question..

Post by max and caddy »

ewenmaclean wrote:Yeah - brake cleaner recommended or Mr Muscle as Lloyd says - can't think of much he hasn't done so that's a good tip ;-)

Sorry to be a pedant but a tdi technically doesn't have a throttle. That's why diesels need vacuum pumps. If you're referring to the anti-shudder valve then it functions as a binary throttle - completely free when running and blocked with ignition off - designed to prevent runaway. Worth checking its operation while you're there for sure though.

The flaps close partially when driving now to cause suction in the inlet so EGR will flow more....the Egr valve, throttle valve and egr change over valve are 3 separate parts....my money is on the change over valve on the back of the engine which incorperates the cooler, some are electric and vacuum and some are just vacuum operated, I suspect it's got both on a 2007 passat...it's a major pain to change it and needs a visit to the dealer for the software adjustment to prevent future carbon build up ( doesn't stop it going wrong in the other 4 ways of course) unless you like struggling up the back of engines I would suggest hiding if these jobs come your way!

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