Cleaning the turbo & power loss A4 1.9 tdi AFN engine 1999

[fantasiagreen]

Hello
All was going well with Audi ownership until yesterday when I suffered a loss of turbo boost - I presume this is limp mode although never experienced it before.

Been doing a lot of reading on here, leading me to the following suspects:

vacuum hose
MAF sensor
boost solenoid
coked up variable vanes on the exhaust side of the turbo

I don't have access to VAG.COM yet although have ordered the appropriate lead today.

I found this which details the dismantling and cleaning of the exhaust side of the turbo. Assuming the worst (as I often do), being that I need to remove the turbo and clean it, I would like to know

How difficult is it to remove the turbo?
Has anyone attempted a dismantling of the turbo similar to that detailed in the link? If so how difficult was it and were loads of o/e gaskets required to put it back together?

The car has done 145k miles and was running well, although I did note that it was feeling a bit gutless over 3k rpm on occasions, which leads me to suspect a MAF sensor covered in oil.

Any thoughts/advice gratefully received. I'll post up what was wrong when its (hopefully) all sorted.

Cheers
Andrew

[fantasiagreen]

I've used my Mityvac brake bleeding vacuum pump to apply a vacuum to the actuator mechanism. I only got about 3-4mm of vertical movement on the actuator rod. I guess it should be more than this?

Although the car drove absolutely fine today.....

[fantasiagreen]

Have done a fault code scan now and the only one I'm getting is:

17958 P1550 - charge pressure deviation

Am I right in thinking that this points towards the variable vanes of the turbo being stuck?

Or could it be the boost pressure regulator? Would this show another code as well as the one I've already found if it was on the way out?

Cheers
A

[Mike McKinstry]

I currently have same fault on passat 130pd(AWX)and just to let you know yes your suspects are correct except the MAF normally just shows itself as poor general running and the MAP on back intercooler to EGR pipe is more usually a suspect.i have changed my MAP and seen no difference.I also believe a vacuum leak would result in limp mode all the time unless it is a leak to the N75 valve so am going to replace pipes to N75 and N75 valve this week.if this fails to sort the problem then it looks like replacement turbo.

Keep me posted on your progress.

Mike

[fantasiagreen]

Well I took it for a long (180miles each way) drive over the weekend and the problem seems to be solved for the moment, in that I cannot get it to go into limp mode even when I change up at > 4000 rpm.

Have changed all the small vacuum hoses anyway (I'd already bought the hose and some of them looked a bit worn out).

Will post again if the problem happens again.

Cheers
Andrew

[Mike McKinstry]

I never did change the N75 as after long roadtrip to N.I things were better making me think VNT mechanism.

However just before hol to france limp became more noticeable again
and going to Le mans got the 250 miles before limp mode with 40 miles to go?This time it would not reset with ignition but next day all ok again.
I then managed to drive the car the 400 miles home without limp mode as i drove under 2800 revs and believe there is a link between this rev range and the fault.
Does anyone know if the N75 could be doing this or is it just the turbo VNT would be at max opening in 5th gear at this rev band?
I have again this week managed to trigger limp by going through this rev limit it 5th along fast motorway and reset in normal manner however have thrashed again in all gears ,lower top speed with no limp?

Mike

[viperwhite]

hi, ive got the same problem. ive had the turbo out but had to put it back in as was going on holiday. its fairly painless really. just disconnect airbox and all pipes etc connected to turbo and exhaust there is also an oil feed drain pipe under the turbo 2 10mm bolts. i found it eaiser to undo the 3 bolts that connect the turbo to the manifold and not taking the manifold off. then its a case of jiggling the turbo round a bit to get it off. took about 1 hour to take off first time, so not too painfull. will do it again and clean when ive got time.

[trickyfocus]

I used the innotec turbo cleaner last week and what a diffrence. No more limp mode in 4th and 5th @3k revs i recomend it for £40 ish

http://www.innotecworld.com/c-1064-turbo-clean-set.aspx

[Sir-Doris]

I had similar problems. Just started one day when overtaking, limp mode and no EML. And it wasnt consistent but generally only happened when accelerating hard in 4th or 5th.

Removing the turbo and cleaning is not so difficult, a few fiddly nuts and bolts but all connections are relatively straightforward. None of the nuts or bolts on either car I did were siezed thankfully but I did prep them a few days in advance with penetrating oil.

Keep a copy of the how to printed and to hand, useful when reassembling the turbo so you get the vanes aligned correctly.

I did mine (1.9tdi AFN) and my dads Passat (1.9tdi AFN) over a weekend. Passat was a bit more fiddly as it had air con pipes in the way.