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View Full Version : Boost leak? Wastegate issue? HALP



DeathLens
12-04-2014, 01:26 PM
Ok so, my fiance has a 1999 Audi A4 1.8TQ, automatic, 220,000km's.

The car has been great for the 2 years or so that she has had it, aside from one, constant, looming thing.

About a year and a half ago I got the car chipped (Unitronic). I did this because the car felt insanely slow...like it was a 2.0NA Jetta. Eventually after running with the chip for a while I discovered a ripped intercooler hose...replaced and noticed a difference, but it was still slow against my 340k+ auto 1.8T.

After installing a boost gauge, it gave me a better idea of what was happening: WOT 2nd gear, boost will creep slowly to about 10psi...maybe 12, and stick. When I say creep, I mean like, 5-6 seconds to boost.

Now I have exhausted boost leaks from what I can gather, the car seems to be solid in that sense.

I have had people tell me this could be an issue with a sticking wastegate. I have also wondered if the cat is bad (due to this rattlesnake noise the car makes on decel that comes from that area).

At this point though I really don't want to tear the turbo out of this thing just to find out it is something else...I suppose that is the game we play though.


Anyone have any insight? Or possibly had a similar issue and can tell me where to start? I would like to get my money out of the chip eventually.


TLDR: Car is boosting incredibly slowly, and will only hit 10psi...no apparent boost leaks. [confused]


Any help greatly appreciated.

Car in question:

http://i1329.photobucket.com/albums/w547/PfaffTuning01/Amanda_zps2f5a0cf3.jpg

10kredline
12-04-2014, 10:23 PM
Two words,Vag-Com. Also, boost leak test.

DeathLens
12-05-2014, 05:23 AM
Two words,Vag-Com. Also, boost leak test.

Forgot to mention that, Vag-Com shows nothing.

I will try the boost leak test.

*UPDATE: Test showed no leaks.

fed0ra
12-05-2014, 07:57 AM
You could remove the cat and check if it's clogged, that could definitely cause your issue. It would also be worth removing the turbo to check that the wastegate flap is opening and closing correctly.

DeathLens
12-05-2014, 04:06 PM
Another update:

Cat is not clogged, scoped it and found nothing substantial. The wastegate works when pressurized...right now I am awaiting the boost pressure sensor to arrive and replacing that. At this point, if this is not the issue then the turbo is cooked.

I will check back when I have the answer, for future reference sake :D

fed0ra
12-05-2014, 09:26 PM
What does Vagcom say for your requested vs actual boost? When I had a bad map sensor it was saying I made full boost but was actually hitting around 10.

BaseDrifter
12-05-2014, 09:37 PM
There is no MAP sensor on OP's car.

OP, don't be so quick to diagnose it as a bad turbo. I went through the hassle of replacing the turbo when I was chasing a low boost problem on my car and it didn't fix a thing. If you want to make sure the turbo can still build boost properly, hook up a vacuum line directly from the compressor housing reference port to the waste gate. This will keep the WG shut and allow the turbo to build boost even if you're stuck in limp mode. Don't push it though, it's very easy to over boost and cause a lean condition. Run it up to 18-20psi as a check.

10kredline
12-06-2014, 10:50 PM
Check your N75 is it's working properly, any codes on that?

alexvanlewen
12-07-2014, 01:39 PM
Car in question:

http://i1329.photobucket.com/albums/w547/PfaffTuning01/Amanda_zps2f5a0cf3.jpg

Jesus Christ, kill this. A giant WTF on those wheels

RallyeBourne
12-07-2014, 01:43 PM
Jesus Christ, kill this. A giant WTF on those wheels
I can't believe I'm saying this, but I will politely disagree. I kind of wish my fiance drove a car like this. The pink wheels on the white car actually looks better than I thought it would.

alexvanlewen
12-07-2014, 02:11 PM
Thank you good sir. I just think it looks too rough, and lacks clear coat

redline380
12-07-2014, 03:27 PM
I'm thinking it really sounds like a wastegate issue. You said it opens under pressure, but at what pressure does it open? and how fast does it close? How hard is it to pull the rod? Is the rod adjusted properly?

My only other idea would be a pre-turbo exhaust leak. Check manifold to head nuts and turbo to manifold bolts for tightness as well as gasket integrity

DeathLens
12-08-2014, 05:12 AM
Thank you good sir. I just think it looks too rough, and lacks clear coat

Oh no doubt they are rough [>_<] They were spray painted probably two years ago...right now they are just a means to an end. She will probably end up with my 18's next spring.

The car needs a big time polish as well, thats getting done in Jan.

Back to the other things: The car has a Forge 007, relatively new so there should be no issues there (not quick to dismiss, but I have never had issues with these in the past). The car is going in and out of my shop being looked at by a tech here, so I cant give exact specifics as to what pressure he was testing the wastegate at, but I will definitely look further into it myself.

As for the exhaust leak, I checked myself a few weeks ago and couldn't see to find anything, thats not to say there is not a leak somewhere though.

Should hopefully be replacing the sensor today and going from there.

Thank you everyone for the tips and suggestions thus far, keeps my mind open to options for fixing it! So thank you!

DeathLens
12-16-2014, 04:03 PM
Ok, update time.

Replaced the boost pressure control solenoid. Car is more responsive, but locks at 6 psi now.

Seems quicker, time from foot to the floor to 6 psi is less, but before it was moving slowly to 12 psi.

The mystery continues.

MetalMan
12-16-2014, 04:20 PM
I didn't see a response to this:


There is no MAP sensor on OP's car.

OP, don't be so quick to diagnose it as a bad turbo. I went through the hassle of replacing the turbo when I was chasing a low boost problem on my car and it didn't fix a thing. If you want to make sure the turbo can still build boost properly, hook up a vacuum line directly from the compressor housing reference port to the waste gate. This will keep the WG shut and allow the turbo to build boost even if you're stuck in limp mode. Don't push it though, it's very easy to over boost and cause a lean condition. Run it up to 18-20psi as a check.

Did you try hooking a line directly between wastegate and compressor reference port? I believe unplugging the N75 should achieve the same result as well. In either case you should see ~5psi and if you don't then that could help with diagnosis.

DeathLens
12-18-2014, 12:02 PM
I didn't see a response to this:

Did you try hooking a line directly between wastegate and compressor reference port? I believe unplugging the N75 should achieve the same result as well. In either case you should see ~5psi and if you don't then that could help with diagnosis.

That was going to be the next course of action.

Had the car in the shop today to check the exhaust side wastegate. Turns out its cracked and very loose.

So the car goes back on the road until I find a used turb to put in there.