Overboost and Limp Mode problem solved.

**Big G.** · 19-03-2008,11:26 AM

Hi All,
After months of overboosting and limp mode, and after changing all the usual suspects - MAF, all solenoid valves, cleaning the EGR, checking for vacuum leaks, taking off the VNT actuator and wiggling it to free it, etc, etc, I finally thought it was time to take the turbo off and have a go at cleaning it. When I got it off the car, it was obvious the VNT was sticking, but I could not feel that when I just removed the actuator and wiggled it while it was on the car.
If you're thinking of buying a new turbo, please think seriously about it first. What would you rather pay, £20 for a gasket kit and a couple of days hard work, or £500 for a refurb or £1500 for a new turbo ??
To be honest taking the turbo off for the first time is a pain in the **** and a very hard job, but once you've done it once, it would be a piece of p!ss to do again.
After taking my turbo to bits and cleaning it up I have not gone into limp mode since, and have covered about a thousand miles. Bear in mind my car is a 53 plate with only 36,000 miles on it and the turbo was sticking. These turbo's are a crap design.

Anyway here are a few photo's and a short video of my VNT mechanism:

Before cleaning.

After cleaning.

and the video:

If you're mechanically minded, buy a Haynes Manual and have a go yourself - you can do it, and it saves you a fortune.
Thanks to all who helped on here with advice and tips, I couldn't have done it without you.

Regards,
Graeme.

**dubcruiser** · 21-03-2008,01:14 PM

Your braver than I am but fair play to you. Is this on a TDi 150?

**Big G.** · 21-03-2008,07:30 PM

Yeah, a TDi 150.

I only started the thread so anyone in the same boat could use it for reference.

Good luck if you decide to do it !

**veedub76** · 22-03-2008,03:37 PM

Anybody tackled this on a 110 gt tdi?What is the MAF ?I'm new to diesel VW'S!

**chris.fulton** · 22-03-2008,06:43 PM

Originally Posted by veedub76

What is the MAF? I'm new to diesel VW's

Have a look at the bottom of this link for some good info

https://www.vwaudiforum.co.uk/forum/s...ad.php?t=30859

**Pev** · 30-05-2010,07:33 AM

There were very useful photos, thanks for taking the trouble to put them on.
I have the same problem on my chipped 130tdi 2003 Bora with 69,000 miles. I have replaced the the N75, sensor just before the intercooler, and the MAF. I took the MAF back for a refund as it made the performance worse, though it wasn't a genuine VW part. I have just accepted turning the ignition off and back on again when it happens (usually on the motorway). Its worse resetting it at night as you briefly lose your lights.
I have been putting off taking off the turbo as it looks such an awkward job with very limited room to work. Its very difficult to even check the vacuum hose down to the turbo actuator for splits.
I only wish people would take the trouble to put photos on here when they are referring to the various sensors and work they have done as it is so helpful to others.

**veedub76** · 30-05-2010,10:40 AM

Have you by chance got anymore pics of how you did this please?

**phil miller** · 30-05-2010,10:48 AM

Great thread mate, I've heard about a company that do an airsol that u spray in after capping the turbo outlet and that's meant to be good aswell

**hibbsy21** · 16-03-2011,11:11 PM

Would this be the same for an A4 TDI? Because mine 'overboosts' at 4000 in 3rd and 4th. and i have a top speed of 80. Changed everything else, boost hoses, cleaned MAF, cleaned intercooler and nothing has worked.

**Big G.** · 17-03-2011,10:54 AM

Hi All,

Just as a quick update on this thread, my turbo worked ok for a good few thousand miles but eventually the old limp mode came back

I couldn't be bothered to take it off again so put up with it for over a year. Eventually I got that sick of nearly being killed trying to overtake things as the car slipped into limp mode, I took the turbo off again. I've got a mate who owns a turbo refurb business so took it there. When he looked at it the vanes were damaged and the bearings shot. He said this may have been down to a few things like a overfuel and "runaway".

In the end I had to bight the bullet and he sold me a refurbed turbo for £300. I put it on and the car has been back to normal ever since. That was over a year ago and almost 10,000 miles more on the clock.

Looking back, I wish I'd done this in the first place and it would have saved all the hassle.