Turbo Not Working

On my way home from work today I noticed that I lacked the usual acceleration that I enjoy and when cruising at 100 km/h (60 mph) on a flat road punching the throttle gave me nothing. It felt like the time I disconnected the MAF to get a replacement - that's why I think it's the turbo.

Once at home I shoveled the driveway (we had alot of snow fall here) and on my drive to pickup the kids the turbo seemed to be back.

What could be wrong here?

Here's some more info:

I am not getting any kind of warning light. It has been very cold here for many days lately (-15C, 5F). We just had that snow storm come through - very light and fluffy stuff so I thought perhaps my air filter is clogged.
The snow screen has been removed. The intercooler intake is free of snow. I did have to barrel down the driveway this morning through about 6" of very light snow - it was really no problem at all. When driving I upshift at 2500+ rpm.

Any suggestions? I'm thinking to check the air filter. If nothing there what could I check next?

Kato said:

Once at home I shoveled the driveway (we had alot of snow fall here) and on my drive to pickup the kids the turbo seemed to be back.

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We call it key off reset...power off and then on resets the limp mode induced by overboost. Hardly the end of the world, Kato. How is OJ doing, BTW?

dieseldorf said:

We call it key off reset...power off and then on resets the limp mode induced by overboost. Hardly the end of the world, Kato. How is OJ doing, BTW?

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OJ - I think he's hiding away in FL somewhere...

Sorry for asking but what do you mean by 'limp mode induced by overboost?'

That sounds like a good guess based on your info. Overboost is caused by either your N75 valve not doing it's job, or one of the various vacuum hoses having a hole in it causing the N75 not to do it's job, or the VNT being jammed, or .....

The boost got too high because the VNT wasn't able to control it, so the ecu cuts power. On reset, it works fine until it happens again.

Kato said:

Sorry for asking but what do you mean by 'limp mode induced by overboost?'

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Next time it happens, just push in the clutch, turn the ignition off, then back on. See if this doesn't work.

Of course, if it starts to happen frequently, then you need to troubleshoot.

When driving I upshift at 2500+ rpm.

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Good for economy, not so good for long turbo life. If your turbo vanes never move through their full range of motion, then deposits can build up and prevent them from moving. That's another reason why the ECM would put your TDI into limp mode.

Try 3000-4200 rpm instead.

TornadoRed said:

....Of course, if it starts to happen frequently, then you need to troubleshoot....Try 3000-4200 rpm instead.

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Thanks for the advice. I suppose I should try and stay current on the board but with two small children I don't make it that on as often as I used to (2000 - 2002) Back then the advice was to upshift at at minimum 2500 rpm and to go through gears upshifting at over 3000 rpm's once and a while.

One more question - If I am getting carbon buildup in the turbocharger will changing my shift pattern (3000-4200 rpm) help 'clean up' the problem. Or is the turbo on the 'downward road'.

Thanks,
Kato

Check the movement of the actuator pump on the turbo.
If this is stuck, it will produce symptoms like that. See TDIFAQ,
and good luck!

Kato said:

One more question - If I am getting carbon buildup in the turbocharger will changing my shift pattern (3000-4200 rpm) help 'clean up' the problem. Or is the turbo on the 'downward road'.

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Yes it will...you should be excercising your turbo regularly, your turbo is not on a downward road just a dirty one. If you bring it into the dealer they will tell you you need a new turbo however all you need to do is clean it... http://forums.tdiclub.com/showthread.php?t=140910
Prior to doing this however most turbo problems are related to a cracked vacuum line or sticky N75 solenoid. Start there first.

TornadoRed said:

....Try 3000-4200 rpm instead.

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Just a quick question.

On full throttle acceleration from standstill don't the vanes on the turbo charger go through a 'full cycle' in the 2000-2500 rpm range?