lack of power - limp mod - Flutter - ?! - HELP!!!

[RicDennis]

My 55 plate 2.0TDI A4 Avant went into limp mode a couple of months back, took it to a mechanic who is also a very good mate...put it on the computer, we had a high reading on the EGR (think thats what its called)

So he removed it and cleaned it out.

Just before we did this i noticed a lack of power...turbo still comes in fine at around 2000rpm but only seems to pull upto 3000ish...then goes flat.

Also over the past week I have noticed what can only be described as a FLUTTER when I let off after the turbo has kicked in...kind of like a dump valve thing?!

And just now the car went into 'limp mode' on my way home, pulled over, restarted the engine and obviously this got rid of the limp mode...

This is very frustrating as I cant figure out what it is...nor can the mechanic.

Overall the car seems to drive fine apart from the lack of power.

any ideas????

[bez101]

what codes did you get when u did the scan ?

[RicDennis]

couldnt tell you the codes as it was a while back now. just a high reading from the EGR valve.

should i take it back and get it on the computer again???

[bez101]

well it would be a good starting point
it may not have any codes stored
but always my 1st thing when i have a prob

[RicDennis]

Morning!

Right car went into limp mode again on the way home last night so took it straight to the mechanic whilst it was still in girly mode...

Put it on the comp - code = 16618 - Boost Pressure Regulation: Limit Exceeded (Overboost Condition)

Any ideas?

[Zaz]

My car's doing the same thing...getting fed up of it now. Dealer carried out diagnostics a few weeks back saying I had to change the inlet manifold and something else....diagnostics suggested some sort of turbo underboost or something...est bill just about £1k.

[RicDennis]

Zaz

If yours is exactly the same as mine then it was the vairable vanes in the turbo sticking due to massive amounts of soot!

see pics:

before:

after:

i had the turbo taken out, stripped and cleaned...it is now running fine again!

(thanks to Pete at PLVS in Oldham)


hope this helps!

[Zaz]

That's quite interesting thanks Ric I've not come across that. Reading some of the other topics I thought this was pretty much related to the EGR valve clogging up...
I wonder if it's something I can have a go at over the w/e...... :-)

[billy-fish]

...an update on the problem I had with the misfire. I was getting a intermittent predicted codel logged by the ECU for turbo underboost. Intermittent limp mode, sometimes after cruising for 30 miles at 75mph.

Had it diagnosed by a mechanic who said the vanes in the turbo were sticking so was looking at a 1500 quid repair. Hmm

Anyhoo. after a bit of pondering and poking about I found a very good article on the net about testing the turbo vanes by pinching a piece of pipe from the vaccuum circuit and attaching it to the vacuum actuator on the turbo and sucking. It was smooth as silk, no a trace of sticking vanes. hmm
Well that actuator passed the suck test, what about the others! whilst I was about it I tested them all.

The one on the Inlet manifold, for tumble/swirl flaps did not operate and I kept sucking without resistance. Hmm

I plugged the pipe and tested the car. It drove the same but no missfire. Well thats encouraging. Stripped the actuator down and found the diaphram perforated. Found a part no. and fixed it for under a tenner. The inlet manifold had to come off again tho to fit it. Just to remind me what a crappy job that is.

The swirl or tumble flaps are called by the ecu to operate at about 1500-2000 rpm to cause inlet turbulance which is designed to aid combustion and produce more power at low rpm . Firstly they were not operating so I was not getting any low down power, secondly it was creating a vaccuum leak which was causing the turbo problems. So the car logged turbo underboost.

This is not the throttle body flap, or runner flap which is motorised, and only some models seem to have these flaps. The tdi 2.0 170 is such a beast.

The actuator is a round black plactic cylinder on a bracket attached to the inlet manifold and can be tested easily with a suck.

I hope this helps someone, maybe you will buy me a beer! lol

The car went great...for a week.

A week later the car completely died 400 yards from home and would not start. Had to be towed to a garage. Injector no. 4 had failed with an electrical coil fault. Part cost £480, repair cost £750.

Apparently injector no 1 was done in January under warrenty and these things are like light bulbs. So looking forward to the other 2 packing up.

Its a good job these Audi's are reliable......

Have fun

Billy