99 Audi A3 1.8T Not Boosting

[adamwatson]

After 3 laps of the Nurburgring I was driving back on the motorway and the car seemed to cough then carry on but it doesn't feel like its producing any boost. It drove 500 miles across Europe without an issue other than being a bit sluggish. It has a bailey aftermarket recirculating dump valve and a big air filter and so you can normally hear the dump valve hissing which you now can't. I pulled over and had a quick look at all the hoses on top of the engine and couldn't see anything split or hanging off.

Where do I start with diagnosing this?


Thanks, have a pic of a car getting air at flugplatz as payment



Adam

[DavidB]

I have the same problem with my Astra. I really noticed this when I a-framed a Micra and it just wouldn't pull it, and uphill I had to give up. It's 1.7 Turbo Diesel and they are pretty rapid on boost.

I've been told to check the actuator - my turbo was new a few years ago. Get a boot gauge to check your boost. If the actuator is open all the time, the boost will escape. It's vacuum operated, and kept closed by this or either a big spring.

[rodney]

do the obvious 1st , cheak for leaks , have you got a boost gauge? if not borrow one to see if its boosting well , spin the turbo by hand to make sure its not seized up , ive had this happen before,.

[zippyobrien]

It's probably over boosted and gone into safe mode. My ibiza cupra used to do this often in the cold.

That or your n75 valve is nakered. ( boost control soleniod).

Get it hooked up to vagcom, these engines have a very good diagnostics systems built In

[bobblegut]

I had that on a seat cupra turbo similar age , and it was a sticking actuator , pain in the as it kept happening piece of curse word .

[DavidB]

How did you cure the actuator?

[bobblegut]

I have no idea other than i was told it was free'd off by the chimps working on it . I'm geussing replacing is best . If i had a turbo car again i wouldnt bother taking it to a garage , even a main dealer , they really know F/A . I would take it to a specialist . I'm lucky in having Owen Developments just down the road from me .

[ChasR]

Without trying to quote other forums I would get VAGCOM/VCDS onto it. Hopefully it will steer you towards the fault, if not a symptom of the fault IME.

If I were a betting man I would say it is one of the following:

Split Boost Hose/seal (I would also check the hard pipes if they are plastic ; does the car have any other issues when driving?)
Leaking vacuum lines
N75 valve
A working stock dump valve (Bailey valves can stick but they can be freeed off easily enough (this is your other option)
Iffy actuator.

However, VCDS should get you closer to the problem ; with my VAG it did with many garages being miles off the mark (as well as some forums with the data from VCDS until careful analysis was taken of it).