[Vwdiesel] Limp Mode Frustration

Sun Mar 4 16:19:19 PST 2012

Couple new details:

I swapped the MAP sensor from my working '02 Golf into the Jetta.

The Jetta continued to go into limp, and the Golf did not.  So I guess this would say the MAP Sensor is ok.

Also, I compared the feel of the actuator between the two cars.  They 
feel the same to me.  I did note that the Jetta's actuator did seem to 
very slowly lose some vacuum while the Golf didn't, but it was so slow I
 figured that either 1) it might be a small leak between a hose and the 
gauge or 2) it was small enough that the computer/N75 could be able to 
compensate.

Maybe I'm wrong on that.

Any other ideas?

Dave Cook

________________________________
 From: Dave Cook <davevw at yahoo.com>
To: VW Diesel Group <vwdiesel at vwfans.com> 
Sent: Sunday, March 4, 2012 3:49 PM
Subject: Re: [Vwdiesel] Limp Mode Frustration

More thoughts/questions from a response I just put up on TDI club.

I have pulled a vacuum on the line from the N75 and felt the rod move.  

To add details from what others have asked:

The intake manifold was cleaned when I had the head apart.  

I also checked that the rod moved at that time on the turbo.

Head was off because it was pushing exhaust gasses into the coolant.  

And a couple questions:

I have heard of people having success blowing the vanes clean by driving
it hard.  Is this at all effective if it is in limp mode and the turbo 
is shut down by the computer?  Do I need to keep restarting it to clear 
limp mode (briefly...) or can I keep driving it hard to try to blow it 
clean even though it is limping?

Also, if the vanes are stuck from crud, will the actuator rod move?  I was under the impression it wouldn't.

Dave Cook

________________________________
From: Dave Cook <davevw at yahoo.com>
To: VW Diesel Group <vwdiesel at vwfans.com> 
Sent: Sunday, March 4, 2012 3:33 PM
Subject: Re: [Vwdiesel] Limp Mode Frustration

I did clean the manifold, and it didn't have a very thick layer anyway.  

I can reach down and move the actuator rod, and when I had the head off I also checked and it seemed to move appropriately then too.  I do intend to set it side by side to my Golf and see if they feel similar.  But it does move, and I can attest that no one has tried adjusting anything since before when it drove well.

Dave Cook

________________________________
From: "dieseltdi at verizon.net" <dieseltdi at verizon.net>
To: Dave Cook <davevw at yahoo.com> 
Cc: vw fans <vwdiesel at vwfans.com> 
Sent: Saturday, March 3, 2012 10:04 PM
Subject: Re: [Vwdiesel] Limp Mode Frustration

Just off the top of my head, it sounds like the VNT vanes are stuck causing an over pressure situation.  If the vanes are stuck they can't modulate the boost pressure.  Another possibility could be a really clogged intake manifold.  When you fixed the other stuff, did you remove and clean the intake?  I also had this problem when I installed the hoses on the N75 wrong.  You might want to closely look at that also.  Just a few things off the top of my head.  I will kick it around a bit more and think about it to see if anything else comes to mind.  Hayden

On Mar 3, 2012, at 9:43 PM, Dave Cook wrote:

> This is a friend's '01 Jetta TDI.  Keeps going into limp mode, sometimes with a check engine light, sometimes without.  Has been this way for a 
> long time.
> 
> Last spring, I replaced all the vacuum lines while replacing the head 
> gasket, timing belt, and a few other bits in hopes of fixing this.  Also
> replaced the N75 at that time.
> 
> Still goes in limp, and does it more often than not at this point.
> 
> I decided to try some more troubleshooting today.  In doing some 
> driving, I found that the ECU would show two different codes after going
> "limp".
> 
> They were:
> 
> 16618 - Boost Pressure Regulation 
>             P0234 -
> 35-00 - Limit Exceeded (Overboost Condition)
> 16492 - Manifold / Barometric Pressure Sensor (G71) / (F96) 
>             P0108 -
> 35-00 - Signal too High
> 
> They were showing up sort of alternatively, maybe a couple times one of 
> them and a couple times the other.  Or a couple one, then the other, 
> then back to the one.
> 
> Once, both popped up at the same time.
> 
> I was romping on it going up hills during this testing.  It only took a 
> couple seconds of heavy acceleration to cause limp to come up after 
> having shut down the car and clearing the codes.  
> 
> I then pulled the MAP sensor from the intercooler.  I noted a oily 
> coating on it, so I cleaned it off with air flow sensor cleaner.  No 
> change on reinstallation.
> 
> I'm thinking the problem might be the MAP sensor, but my friend doesn't 
> want to throw money at the car hoping something fixes it.  
> 
> Any other thoughts?
>  
> Dave Cook
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