Power loss when under load

[alexandjen]

Has anyone else had this problem?

Towed the caravan approx 40 miles last weekend, every time I started to climb a hill on the motorway I suddenly lost power as though the turbo had switched off - speed dropped off dramatically......

Turned ignition off and on quickly and all seemed fine again until the next hill.

It only happens when towing, never solo - is there a valve which switches the turbo as it seems like I'm resetting something when I cycle the ignition via the key?

Thanks in advance for any advice

[gac]

You're hitting limp mode, sounds like it's probably sticky turbo vanes IMO. As you put the car under load to get up a hill with a heavy load, it's trying to increase the power, too much air is going through the turbo as the variable vanes are sticking and not closing quickly enough and the car is detecting overboost and just cutting the turbo out altogether. Long term fix is a turbo clean, but in the short term the "Italian tuneup" can help. Take your car for a long run, warm everything up and keep putting your foot gently to the floor and let it off again (causes different load conditions and causes the vanes to open and close).

Alternatively if you can find someone with VCDS then there's a VNT exercise that can be done which just cycles the vanes from one extreme to the other. That will probably also help.

[mbames]

Towed the caravan approx 40 miles last weekend, every time I started to climb a hill on the motorway I suddenly lost power as though the turbo had switched off - speed dropped off dramatically......

Punishment for belonging to the EvilCaravanTowingGang

Sticky vanes (or maybe MAF, n75, vacuum leak). If you pull off the vacuum hose between the n75 and actuator on the turbo and suck on it, you should be able to exercise the vane controller on the turbo manually. If you have thing arms you can get one down the back of the engine past the EGR assembly and feel the control arm moving. It should be nice and smooth. If you can't get your arm down the back, you can take the undertray off and test from underneath.

Alternatively if you can find someone with VCDS then there's a VNT exercise that can be done which just cycles the vanes from one extreme to the other. That will probably also help.

How do you do this with VAGCOM?

Edited 1 September, 2011 by mbames

[gac]

Connect it and start the engine, Basic Settings, and then group 011. Your RPM should rise to about 1400, and you'll hear the pitch of the turbo changing. Also on the VCDS display you'll see the duty cycle percentage changing, and you should see the requested and actual pressures changing. It runs for about 10 minutes, cycling between each extreme on the vanes about once every 4-5 seconds, then stops and idles as normal.

[alexandjen]

You're hitting limp mode, sounds like it's probably sticky turbo vanes IMO. As you put the car under load to get up a hill with a heavy load, it's trying to increase the power, too much air is going through the turbo as the variable vanes are sticking and not closing quickly enough and the car is detecting overboost and just cutting the turbo out altogether. Long term fix is a turbo clean, but in the short term the "Italian tuneup" can help. Take your car for a long run, warm everything up and keep putting your foot gently to the floor and let it off again (causes different load conditions and causes the vanes to open and close).

Alternatively if you can find someone with VCDS then there's a VNT exercise that can be done which just cycles the vanes from one extreme to the other. That will probably also help.

Thanks, I might get some Innotec Turbo Cleaner and see if it helps

[alexandjen]

Punishment for belonging to the EvilCaravanTowingGang

Sticky vanes (or maybe MAF, n75, vacuum leak). If you pull off the vacuum hose between the n75 and actuator on the turbo and suck on it, you should be able to exercise the vane controller on the turbo manually. If you have thing arms you can get one down the back of the engine past the EGR assembly and feel the control arm moving. It should be nice and smooth. If you can't get your arm down the back, you can take the undertray off and test from underneath.

Thanks, I'll give the pipe trick a go at the weekend, my arms are too big so will have to attack it from underneath, oh and less of the micky taking with regards to us caravan owners please

[mbames]

Thanks, I might get some Innotec Turbo Cleaner and see if it helps

I would exhaust other avenues first.... (waits to shot down in flames)

[Volvomeg]

I have a friend with a ford galaxy with the 115bhp Vw engine in it doing exactly the same thing,

Not had chance to have a look at it yet but going to try an italian tune first

[gac]

I'm told it can have good results, however the thing to remember is that you want to unstick the VNT mechanism, and it's the movement of the vanes that'll do this. Rather than just going for a long blast up a hill with your foot to the floor (instant limp mode) you want to vary the load gently between no load and high load to get everything moving gently. Otherwise you might not actually be freeing anything up at all.

[mbames]

I'm told it can have good results, however the thing to remember is that you want to unstick the VNT mechanism, and it's the movement of the vanes that'll do this. Rather than just going for a long blast up a hill with your foot to the floor (instant limp mode) you want to vary the load gently between no load and high load to get everything moving gently. Otherwise you might not actually be freeing anything up at all.

Exactly. Sometimes the vanes don't get jammed, but instead the control ring side of it gets jammed up. Easiest way is to manually apply a vacuum to the actuator, or use VAGCOM with the instructions posted above.

[alexandjen]

Exactly. Sometimes the vanes don't get jammed, but instead the control ring side of it gets jammed up. Easiest way is to manually apply a vacuum to the actuator, or use VAGCOM with the instructions posted above.

Excellent advice guys - any idea which pipe I need to suck on (carefull) coming from the N75 or is it obvious?

[mbames]

Excellent advice guys - any idea which pipe I need to suck on (carefull) coming from the N75 or is it obvious?

The lower left pipe from the n75. it runs across the bulkhead and then clips into the intercooler pipework and runs down to the turbo.

It might take a good suck though, try not to get too red in the face

Edit: correction to indicate which pipe runs from the n75 to the turbo.

Edited 2 September, 2011 by mbames

[alexandjen]

Thanks again, will update when I've tried it if I haven't been rushed to hospital

[mbames]

It is also worth checking the pipework can hold a vacuum too.

Once you have sucked and released the actuator should return to its at rest position. if you blow down the pipe and it moves, then that suggest something is a bit jammed.

[alexandjen]

Top left pipe from the n75. it runs across the bulkhead and then clips into the intercooler pipework and runs down to the turbo.

It might take a good suck though, try not to get too red in the face

Mmm mine is the lower left connection on the N75, is this right? and when I suck on it nothing happens, it holds a vacuum though as it sticks to my tongue (carefull) Can you confirm that the pipe is supposed to be on the top of the N75 and what the label is on the outlet please?

Is it supposed to have a small round filter in line with the pipework close to the N75?

I can't blow down it at all

[mbames]

Sorry, I was wrong, it is the lower pipe on the left side. I'll edit my post above, so as not to cause confusion to anyone else reading this thread at a later date.

Ideally you need to be under the car so you can feel the actuator arm on the turbo move when you suck on the pipe (as you said you could not get your arm down from the top).

The blowing thing is for only after you have applied a vacuum, to see if the actuator can return to its natural position, or if it is getting stuck on its return and needs some additional help.

The "filter" is a oneway valve.

Edited 2 September, 2011 by mbames

[alexandjen]

Thanks for confirming, I'll get her up on the ramps tomorrow so I can get to the actuator arm

[alexandjen]

Had her up on ramps this morning, disconnected the vacuum pipe from the N75, unclipped it and dropped it beneath the car so I could suck on it and watch the actuator arm at the same time.

Well I sucked as hard as I could and it barely moved, probably about 1mm if that.

The pipes appear to be holding a vacuum as I can disconnect them at random locations and hear the vacuum escaping, I tested the vacuum pipe to the turbo to make sure it wasn't blocked as well.

Couldn't find any loose, split boost hoses either so I am assuming the inside of the turbo is gummed up.

Before any of this I read the codes and got 17978 & 17964

It did cut out once after starting last week but hasn't done it since

I also removed and cleaned the N75 with contact cleaner and checked the one way valve wasn't blocked just to make sure

So it looks like I either need to get it on VCDS, take it for a long drive and exercise the vanes or clean the turbo.

[mbames]

Well I sucked as hard as I could and it barely moved, probably about 1mm if that.

:(

I think that points to the current problem - either the vanes are jammed, or the control ring is.

There may be a secondary issue to this - driving like a granny so the vanes don't get to move, or a lack of vacuum change being applied to the actutator on the turbo (ie. n75 failure), or a vacuum leak somewhere.

So it looks like I either need to get it on VCDS, take it for a long drive and exercise the vanes or clean the turbo.

If you try using VCDS to do this, you ideally need to observe the actuator to check it is actually moving. I would suspect you won't get full travel (otherwise you won't be getting limps, unless it is just slow to react). If the movement is slow you might find exercising it is enough to sort the problem out, but I would not consider it a long term solution.

FWIW, since I did my elephant mod and blocked off the EGR, my anti-shudder assembly as remained lovely and clean, so that must be a benefit to the turbo (no oily-air passing through it).

Edited 10 September, 2011 by mbames

[alexandjen]

Yeh maybe I ought to kick it more often rather than trying to beat the world record for mpg around town

I did the elephant mod and blocked the egr vacuum approx 18 months ago so should be getting cleaner air through the turbo.

If I drive it and try to exercise the actuator, do I drive at motorway speed in say 5th gear and just slowly accelerate and decelerate to get the turbo kicking in or is it more accelerating up through the gears which has an effect?

[mbames]

I think it is most about driving through the rev range, but don't quote me on that. I can easily drive and never go over 2-2.5k rpm, where as I am sure getting close to the red line (gently in say 3rd) and again in 4th (if on a motorway ) gives then actuator longer to move, rather than say a quick 2 second blast.... I would say on the motorway, do a bit of 4th gear work too... a bit of variety is always good rather than just sitting at 2100rpm @ 70mph in 5th gear.

Elephant mod gives you clean air through the turbo, while the EGR block stops the inlet manifold and EGR assembly looking the the inside of a tar factory.

I find these darker evenings are more fun. Find a roundabout with an uphill exit. Boot it off the roundabout with some unfortunate person following, and stay in low gears..... admire the clouds of black coming from the exhaust until the car behind crashes through a hedge because they can't see where they are going. If I have a gentle motorway drive, of say 200 miles, I like to that on the final leg of the journey home.

[alexandjen]

Yeh, I must admit I am guilty of getting into 5th as quick as I can, no matter what kind of road I'm driving on

Will try and use more of each gear and take it gently to the red line every now and again