A4 B6 turbo problem

bcmf

No real problems when driving normally.
Gets up to speed,cruises fine etc except when I need that extra bit and and start to get the rev's up towards 3000 it seems to 'stall'. And by 'stall' I dont mean the engine cutting out. It almost seems like the turbo stops and wont go any further.
No signs of black smoke and once I get back down towards 2500 rpm it ticks along soundly.
Regulary 'open it up' to try and stop build up.
I know I will prob have to get it plugged in to see what fault comes up.

Anyone with any thoughts?
MAF? Boost control valve?
Mr. muscle down the throat of the turbo?

darragh o meara

Sounds like its in limp home mode. Does switching the ignition on/off clear it momentarily? A diagnostics check will give you an idea.

I've looked at a few of these with similar problems and it turned out in most cases to be a boost control valve. First thing I'd do is take off the engine cover and look for a disconnected or damaged vacuum pipe. Might be a case of a disconnected pipe.

bcmf

Hey darragh,
Thanks for the reply.
I dont think its in limp mode as it only happen intermitently, maybe a bit more then that.
But say during my commute to work ,circa 30km, about 80% on motorway it cruises fine at 100 -120 kph but if I need to blast it ...it kinda gets to circa 3000rpm then hesitates then I drop down to normal rev/speed without any issues. As I said no noticeable black smoke.

hiltan

I think vehicle needs to go for service and garage guy identify the issue.

bcmf

hiltan wrote: »

I think vehicle needs to go for service and garage guy identify the issue.

I will check all the hoses first then if nothing seems out of place then will bring it someone to be scanned.

darragh o meara

bcmf wrote: »

I will check all the hoses first then if nothing seems out of place then will bring it someone to be scanned.

Yeah, Its a handy enough job for even the most amateur of lads. Just remember not to pull too hard on any of the pipes as some of them won't have clips on them and may come off easily.

Have a look for one of these valves. It will have a vacuum pipe from the actuator on the turbo connected to one side of it. Ive found that the pipe from the actuator can perish over time and cause the problem you described above. Have a feel of the pipe and see if you can find any noticeable damage or even better if you can pull the pipe off you'll get a better idea of its condition. Its the first pipe I check myself when given a passat with this issue. In fact I only replaced that pipe just the other day on a passat and its flying ever since. Any good motor factors can give you a lenght of this pipe if you need it, Its a 3.2mm int diameter pipe on one end which passes through a plastic connector that brings it up to 5mm on the other side.



You mentioned about black smoke, Well you wont get that at all really from this fault. In most cases I've seen the engine management light in the dash doesn't always come on but the car still goes into limp home mode. This is where it drives ok up to about 3000 rpm then just stays there. The turbo wont give anywhere near the pull it usually does, its a killer as I've had it happen overtaking cars and it aint fun when you've got something coming against you.

bcmf

Really aprecieate the help darragh.
Apologies on misinterperting the limp home.
Deffo cant get above 3000rpm after a couple of times of asking for a bit of poke.
a google of it threw up a result that is suggested a road test to do and is leading to either a faulty pipeor MAF fault.


Just thinking a few weeks back that I had an issue with brake boost. My mechanic said he couldnt find fault with master cylinder so we went with booster unit itself. When we played with a pipe it seemed to help the problem so we did a fix on that (the booster unit was €300)
The problem hasnt totally gone away but would they possibly be related as the 2 seemed to have occured around the same time!?!

darragh o meara

It could very well be a vacuum pipe if that's the case. The brake system has a vacuum connection to help with the braking. This vacuum also opens and closes the waste gate on your turbo effectively turning your turbo on and off. If there's a leak then its not going to open the wastegate enough to give it the boost it needs which results in a P0299 fault code which is a fault for under boost which when it gets logged puts the car in limp mode.

If I were a betting man I'd say you could have a problem with a vacuum pipe being perished.

bcmf

Yeah it's starting to point towards that isnt it.

I have a day off nxt wed wed so will get stuck in then.
Will take off the egr as well and give a soak.
If it turns out to be a pipe whats your opinion on Mr. Muscle to clean out deposits on turbo/egr...obvious;y sprayed in after the MAF sensor!
Will be doing a good bit of towing over the summer so wanna have it up to scratch.
When I bought the car 18mnths the guy told me he had changed the turbo and a quick call to the garage confirmed this.

bcmf

OK. A quick rummage at the pipe and straight away I found a cloth covered pipe not connected.
Now the small cloth covered pipe running from what seems to be the actuator on the egr.
Where is this supposed to plug into?

darragh o meara

bcmf wrote: »

OK. A quick rummage at the pipe and straight away I found a cloth covered pipe not connected.
Now the small cloth covered pipe running from what seems to be the actuator on the egr.
Where is this supposed to plug into?

Send me a pic.

bcmf

JUst sent you a pm