NefMoto

Hey everybody,

I have been trying to track down this issue I have been having. First, some details about the car.

-2004 B6 A4 1.8T 6MT
-APR Stage 1+ (KO3 and TT225 injectors)
-Forge DV

I have only had this car for about 4 months now and I have been getting a P0234 Overboost code as well a limp mode.

This is what I have done so far:

-replaced the N75
-unplugged N75 and drove to show that the wastegate was opening under spring pressure (wouldn't boost past 5 psi)
-replaced the leaky (leak was small) N75 hoses
-replaced the torn APR DV with a Forge DV

At this point, I was frustrated and under the advice from someone on Audizine, I unplugged the MAF to see if the car still went into limp mode. It did not. So I replaced the MAF. After a day or two, it went into limp mode again and logged the P0234 code.

I tried contacting APR multiple times and they were no help. I took logs according to their support page. The files are attached.

What is interesting is that the car did not go into limp mode during the pulls. I have yet to experience the limp mode during WOT. It seems to happen only during part throttle. Maybe it just needs an adaptation and/or cleaning?

If you guys have any suggestions, let me know. I am a loss right now and would really like to avoid bringing it to a shop...

P0234 is actually an underboost condition in that file..

http://nefariousmotorsports.com/forum/index.php?topic=7524

Not sure that helps you any, but it might.

Interesting. Guess it makes sense since I have never seen boost go past 18psi.

Thanks for the link, but I am still a bit of a noob, so what would be a reason for the car to go into limp mode? And why would it do that for an "underboost" is that supposed to protect the engine in some manner?

It is there to protect the turbo in case there is a large boost or DV leak or some such and the turbo is being over taxed.

Next step is to log block 111 (i THINK)

Okay. Thanks! I had already checked for boost leaks, but I guess it wouldn't hurt.

Missed this yesterday. Any other blocks that I should log with 111?

Also, is the N75 duty cycle normal in the other logs that I posted?

No, they're maxed out.

which means 111 is likely maxed out.

which means your wastegate isn't closing all the way, you have boost leaks, your inlet is collapsing, you have clogged cats, or your turbo is dying.

If you have boost gauge you can disconnect the wg line and see what the turbo will do (CAREFULLY!)

I'm really hoping it's this. FWIW, the car has a crappy OE style cat that the PO put on. Maybe it's clogged again? Not sure.  ???

Also I have a Forge TIP so I don't think it's collapsing.


I do, that's how I could tell it wasn't boosting past 5 psi when the N75 was disconnected. I'll try that and report back. What am I looking for when I do this? With the wastegate line disconnected, wouldn't it act the same as if the N75 was disconnected, or would it force the wastegate closed?

With the wastgate line removed, it will remain shut and the turbo will spool until something brakes.  Remember it's a K03s and will spool very quickly.  Keep an eye on throttle pedal position and do a pull in third.

Watch for boost shooting over 20000000000psi.

Okay, gotcha.


(https://38.media.tumblr.com/0eaf69a38d56c116001163902cfbd4ca/tumblr_inline_nbebb9vQ8D1r8l6sh.gif)

Okay. So I took a quick spin with the WG line disconnected and it stopped boosting at around 18psi like normal... I did a few 3rd gear pulls and it never went past that. So idk. I'm going to do a log of block 111 in a few minutes.

That isn't normal. With the wg line disconnected it should overboost like crazy.

Also, I assume it didn't hold to redline either...

I meant normal as in that's what it boosts to when the WG line is connected.

It didn't build boost like I expected at all. It spiked at 18 and then tapered to about 14. So, no it didn't hold to redline.

Does this mean the waste gate actuator is bad?

Just for S&G I put the WG line back on and unplugged the N75. It didn't boost past 5 like usual, except it spiked at 10 and then tapered off. So, I don't know what the f-ck is happening.

Waiting for the laptop to charge and I'll do a log of MB 111.

Maybe. Maybe not. But something is definitely bad.


I'm guessing you'll see when they max youll throw P0234...

I just got back from logging. It went into limp mode during one of the runs. It wasn't WOT. I'll post the files in a few minutes.

Here's the files. Run #3 was when it went into limp mode.

wg is maxed, plus any time you see those PID trims above 7 or 8 you are done.

What can we deduce from the 111 values? N75 duty cycle is maxed, so it's working overtime to meet requested boost, correct?

Yes. Not good.

Some things you might want to check

Intake/exhaust restriction
Boost leaks
Properly sealing internal disc of the wastegate. Could be missing altogether, could have mis-adjustment of the rod.

You definitely should boost higher than you are with the wastegate disconnected. That, or the turbo is on it's way out.

I have a test pipe coming in to see if the cat is clogged. While I'm installing the test pipe, I can check the sealing of the disc for the wastegate.

I'll test for boost leaks again. It's been a month or two since I last tested for boost leaks.

Hey everybody, it's been awhile since I updated this, but I installed the test pipe. Still need to do some logs to see if there is any improvement, but in the driving that I've done around town, it has gone into limp mode once or twice under similar conditions as last time.

Not surprising. 95% dc and the boost you're seeing is bad news.

I just wanted to say thanks to everyone who has been helping me with this issue. Did some more logs with the test pipe and it's the same story as before.

So, now I'm on the hunt for either a low mile KO3 or KO4 since I already have the TT225 injectors.

I guess it's not too surprising that the original turbo is starting to have troubles, the APR tune was put on when the car was only a year or two old by the PO. Asking the turbo to boost to 18-20 psi for 130k miles compared to the stock 8psi is asking a lot I guess.

Would you guys think a KO3 with similar miles as mine that was only used with a stock tune be okay or would it have the underboost problem?

Just look for a solid, clean looking turbo with very little play in the shaft.  Some slight side-to-side play is acceptable, and I mean slight.  No in and out.

As long as its clean looking, it should be healthy.  Remember if you go K04 you need manifold, some lines, new TIP, etc.

Yeah, I ended up going with a KO3. A KO4 wouldn't really be worth the small 10 HP 15TQ difference over the current APR tune I have. Even though I already have the TT225 injectors, I would still need the turbo and software which would be anywhere from 500-700 depending on what deals I could get.

I got a good deal on a used KO3 from a fellow member on Audizine. No shaft play and never tuned. So hopefully that will fix my problem.

Okay, another update. Now that I'm done with finals, I decided to tear into the car and swap in the turbo. With my old turbo on the bench I inspected it to see what the issue was. It has very little side to side play and no in and out. After looking it over I believe I found the issue:

(http://i.imgur.com/SrCLVKf.jpg)

(http://i.imgur.com/QnbH5Gp.jpg)

Two fairly large crack in the waste gate where the flapper seals. I would imagine this would affect the sealing of the waste gate and cause the N75 duty cycle to max out trying to keep this closed (to no avail)?

Looking at the new used turbo, it seems to have slightly more side to side play and still no in and out. However, where the flapper seals it looks much better. I forgot to take pictures of that.

Would it be safe to say I have found my problem and should go ahead and install the newer turbo?

take the housing off the new one and put it on the old one , bobs your uncle ! ;D

Those wastegate cracks shouldnt keep your turbo from making boost unless the wastegate isnt closing at all. Our TT k03 had these cracks (well I even guess all turbo's that have over 200.000km) and happily spooled to 22psi. Would blow itself into bits without wastegate control. Have you done a pressure test on the inlet side? And hows the compressor doing, is it in good shape?

I did notice that the disc did not close very firmly against wastegate.

How would I go about pressure testing the inlet side?

Take off the first silicone connector that is fitted to the compressor outlet of your turbo. Plug it with a 2" O.D. cap with a connector for pressurized air (I have made a very simple version with just a car tire-valve). Take off your oil filler cap and apply pressurized air to the tire valve (or connector) untill you reach your boost pressure (I would want to see at least 20psi), then go and listen for air leaks around the engine. You can also have this done at a garage, where they will usually include smoke into the system so leaks get visible. If your system can hold 20psi with only gargling from the valve cover, your turbo is the problem. If not, repair and test again.

Okay, so I feel dumb for not trying this earlier. I took the air nozzle from my air compressor, adjusted the regulator to about 6psi and connected it to the wastegate port with some vacuum line.

On the old turbo, the wastegate would not open under 6psi and I could hear and feel air rushing past the diaphragm. It wouldn't open until I adjusted the regulator to 20 psi.

However, on the new turbo, it opened right up at 6psi and there were no air leaks.

So now I feel pretty confident I found my problem.

Good news, you could not have replaced the actuator without removing the turbo anyway  ;D

Ugh. Just finished up swapping the turbo and one of the coolant lines are leaking. The car doesn't go into limp mod anymore at least. I think it might be the coolant feed line. Used new copper washers and made sure it was torqued to spec. I guess that wasn't enough. It's also a fairly large leak, took it for a quick spin and the coolant tank is only half full now.

I'm waiting for the car to cool down a bit and I'll get under it and see where it's coming from.

I was just going to say check the actuator arms you can generally attach a hand pump and observe / adjust normally.

Also check Id of hoses and their wear.

Gets got though after a few runs so mark ur original spot!

There will be threads all over on this on Google (wg Check)