A4 B7 Overboost problem

Posted: Mon Sep 17, 2012 4:09 pm

Recently my 2005/5 A4 B7 2.0tdi 140 has started to go into overboost and then subsequently 'limp home' mode. If i flick the ignition all is well again until i boot it ( usually uphill) and it happens again.

Put VCDS on it and comes up with:
1 Fault Found:

000564 - Boost Pressure Regulation
P0234 - 000 - Limit Exceeded (Overboost Condition)
Freeze Frame:
Fault Status: 01110000
Fault Priority: 0
Fault Frequency: 1
Mileage: 233288 km
Time Indication: 0
Date: 2111.15.31
Time: 31:63:63

Freeze Frame:
RPM: 3150 /min
Speed: 128.0 km/h
Load: 82.4 %
Voltage: 13.91 V
Bin. Bits: 00001000
Absolute Pres.: 2509.2 mbar
Absolute Pres.: 2590.8 mbar

After talking to a couple of people and doing a bit of google i changed valve N75 - which made no difference!

anybody help????

thanks

Mark

Posted: Mon Sep 17, 2012 7:23 pm

the variable vanes inside the turbo have gotten a bit stuck because of soot build up.... the vanes need to be able to move to control the boost...
the can easily cleaned by a skilled mechanic...

this guy will be able to do this for sure...
http://www.darksidedevelopments.co.uk/

perhaps you can talk to Ryan if he knows someone in your area
who can help you out...

JW

Posted: Mon Sep 17, 2012 7:53 pm

I didn't save the VCDS paperwork from a similar experience I had with my B7 3.0TDI. I'm fairly sure though that the reading was very similar, if not the same as yours.

It was fine for a few months after buying it but limp mode came in after I accelerated hard in 2nd gear. Did it a few times. Ignition off then again cleared it.

I took it to Lucus in Bristol who are well known around here for sorting out diesel related oddities.

Turns out the remap that was on it which, was deemed as 'awful' so they adjusted it around and bit and gave the car back. Totally fixed.

I took the machine to another mapper who said that it was one of the worst maps he'd seen. Remapped properly and it's been good as gold for well over 10,000 miles.

Just thought i'd throw that in just in case your had previously been mapped..

Posted: Tue Oct 02, 2012 1:48 pm

So........ found a very good small indie garage who had a look at this for me - and as Struikie said earlier, my problem was that the vanes were sticking which was verified when the turbo was removed...SOOOOOOO much crud!!! - unfortunately there was also a fair amount of end play in the shaft which needed dealing with, so i ended up getting a new (reman) turbo at a very good price ( i thought it was anyway) of £210!!

Everything back together and took her for a drive...EXACTLY THE SAME.

still coming up with the same fault - any more ideas anyone?

The turbo would have needed sorting very soon anyway so i'm not really bothered about buying one...just curious as to what my problem is
going to dismantle the EGR and clean all that out this week.

regards

Mark

Newbie Joined: Aug 12, 2014 Posts: 1

Mark, did you find the root of this issue ?