Please help with engine power loss issue

[jb1970]

Took my 2015 RS7 out to get gas this morning and found it is seriously underperforming.
For the first 10 miles or so I could hear a whirring sound when pressing the gas pedal and there seems to be very little power.
The whirirng sound went away, but still have very little power.
It feels to me as if the turbos have simply stopped working.

It has an APR tune and I reset it to factory tune but that did not help.
The only issue I have had were fault codes for random misfires now and then.

Any ideas as to what might be going on?
It was fine when I parked it last night.
No CEL or fault codes.

[VVG]

Took my 2015 RS7 out to get gas this morning and found it is seriously underperforming.
For the first 10 miles or so I could hear a whirring sound when pressing the gas pedal and there seems to be very little power.
The whirirng sound went away, but still have very little power.
It feels to me as if the turbos have simply stopped working.

It has an APR tune and I reset it to factory tune but that did not help.
The only issue I have had were fault codes for random misfires now and then.

Any ideas as to what might be going on?
It was fine when I parked it last night.
No CEL or fault codes.

My first guess is a boost leak of some sort. At some point you will likely throw a code. Do a visual check (so far as you can) of the entire airflow pathway from intake to intake manifold. Have someone else rev the motor while you listen at the engine with the hood open and the engine cover off to see if there is something obvious also.

A number of years back, I had a hose split smack in the middle of a drag strip run on my old Stage 3 B5 S4. Instant power loss.

[F16HTON]

Took my 2015 RS7 out to get gas this morning and found it is seriously underperforming.
For the first 10 miles or so I could hear a whirring sound when pressing the gas pedal and there seems to be very little power.
The whirirng sound went away, but still have very little power.
It feels to me as if the turbos have simply stopped working.

It has an APR tune and I reset it to factory tune but that did not help.
The only issue I have had were fault codes for random misfires now and then.

Any ideas as to what might be going on?
It was fine when I parked it last night.
No CEL or fault codes.

Car will not make any power until the oil is up to temp. If you pushed it in the first 10 minutes of driving, it most certainly pushed back at you. There is an electronic LED redline on the tach which lets you know when you can push the car and when you cannot :)

[jb1970]

The car is definitely warmed up now, but the problem is still there.
Even when temps were -10F the car did not behave like this. Its 60F today.
It sounds fine, but it has acceleration under full throttle that feels comparable to my wife's 4 cylinder Honda Accord.

I have the APR dongle and mobile app.
Any advice on what I could log to help diagnose the problem?

[repnaudi]

Sounds like a boost leak. That will cause u to loose power and also hear the whine of the turbo. Check for leaks

[jb1970]

Still have the problem today.

Lets see if this picture of engine speed and boost pressure shows up.

[IMG][/IMG]

[VVG]

Still have the problem today.

Lets see if this picture of engine speed and boost pressure shows up.

[IMG][/IMG]

Is this actual total pressure or only boost pressure? It appears to be actual total pressure since when you are not revving the engine, you are at atmospheric or 1000 millibars. If this is the case, your maximum boost is 200 millibars or about 2.9-3psi. So that seems to be your problem. You are not holding boost. This could be a boost leak, or a problem with the wastegate actuators opening prematurely, or the turbos themselves. The last is less likely, as this would imply that both turbos have blown simultaneously. Even with one faulty turbo, I would expect to see more than 200 millibars of boost. There could be other issues, but this is what first comes to mind. In any case, you definitely need to run run a diagnostic. Again, my knowledge base does have holes in it, so if I am missing something, I always welcome for someone to educate me. Good luck and keep us posted.

[jb1970]

The title of the graph came directly from the log file, I didn't modify it.
It says Boost Pressure (actual).

I will be taking it to the APR dealer tomorrow.
Will he be able to see more information than I can access with the APR mobile app?

I hope I am not causing further damage by continuing to drive it.
I am amazed that the car is performing so poorly and yet there are no warning lights or fault codes.

[Clipse3GT]

It sounds like a boost leak. However, I would pull all 8 plugs and have a look if the electrode tips did not get detonated off common in higher powered turbo cars. If it detonated some spark plug tips off they could have went into the turbo and destroyed the turbine and that can be an issue. It can be caused by high amounts of octane booster or poor fuel typical of 91 pisstane... detonation is usually a killer of turbo cars. Either caused by fuel, spark, or a mechanical issue.

[BlueSVT]

Here's a thought... could be a boost leak! lol

Curious what they find... keep us updated!

[jb1970]

I wonder if this is the problem with my car?

http://www.audiworld.com/forums/rs-7...mlins-2878893/

[jb1970]

The spark plugs were removed and did not have any visible damage like broken tips.
They are going to put in new plugs today and see if that helps.
If not maybe its the fuel pump as in the above post.

[bhvrdr]

The spark plugs were removed and did not have any visible damage like broken tips.
They are going to put in new plugs today and see if that helps.
If not maybe its the fuel pump as in the above post.

You can log your rail pressure. I'd also get another set of logs. The logs you posted do not have any measure of load on them so it is impossible to know what your car should have been boosting at. If you were not loading the car it shouldnt have been producing much boost anyways. Your log looks like you were driving around town. The log should be a full throttle pull in third gear from 2000rpm to redline. I'd grab requested and actual boost, throttle position, engine speed, rail pressure, knock retard cyl 4 and cyl 8, wastegate duty, and actual timing. Make sure to use grouping and turbo mode if using vag com.

Mike

[jb1970]

The car is at the repair shop now.

But here is some more data from the log I captured after it started misbehaving.
It is a log of somewhat normal driving.
Although I did floor it a few times the car did not respond as it should.
Anemic acceleration and revs building rather slowly (perhaps 30-40% of normal rate).

[bhvrdr]

Unfortunately part throttle logs are going to just be a mess. Your boost is going to be low under part load and it should be low. Under part throttle timing and timing corrections go crazy as well (when lifting). You need a single full load run from 2000rpm to redline. The logs you posted arent going to give any useful info :(

https://www.goapr.com/support/datalogging.php

Mike

[jb1970]

Well hopefully the the repair shop (which is an APR dealer) will know what to log and get to the bottom of it.

They told me yesterday that the software was indeed calling for lots of boost, but it was simply not being developed.
So it was either a huge leak or both turbos blown (unlikely).

I thought there might be something obvious in the log I have since I am looking for something very wrong, rather than trying to figure out something subtle like why a car is making 600hp instead of 650hp.
I think the car is making 200hp at the moment.
For example, would the graph of fuel rail pressure shown tell you if the fuel pump was bad or not?

[bhvrdr]

The logs under part throttle will be useless for diagnostics. You're not requesting much fuel or boost when you arent under load so not likely to be able to see fuel or boost issues on those logs. Honestly, you really do need a single full throttle run from 2000rpm to redline. There's a reason APR gives directions on how to datalog :) Your city driving logs are going to show all kinds of funky things that will not be reflective of a true issue. Let me give you an example, your ignition angle log spikes up to almost 50 degrees. That would be insane if it were meaningful but because it is not a WOT log it is expected. Another example is your boost being way low. Again, who knows if that is an issue because it was likely under low load where you wouldnt be making much boost anyways. Same with fueling. You are only torture testing the fuel pump under full load.

Mike

[jb1970]

Update:
The car was flashed back to stock and still has the same problems.
Other than the car is running very rich, they are not getting many ideas as to what exactly is wrong yet.
Running rich and not generating boost, but don't know why.
Hopefully tomorrow will bring some clues.

[bhvrdr]

Makes sense for a vacuum/boost leak. Now its hunting it down. Smoke test may help find it.

Mike

[jb1970]

I believe a smoke test was the first thing they did.
Don't know much about this.
I believe they said they were only using 1psi and it can be hard to detect as its slow to get through the system.
Looking on Youtube I believe I saw people using 5 and 12psi for a leak test.
Not sure if these are completely different tests.

[bhvrdr]

yeah, they need to use a higher pressure like 15psi.

Mike

[jfeger]

I just had the same symptoms on my stock 2013 S7. My issue was harder to decipher from my "seat-dyno" because I only had the car for three days. However, I felt like it wasn't what I expected from an S7 and just kept going hard on the pedal and eventually the EPC light came on. It took me a couple of days of driving and pedal stomping to get the light to come on. It wont happen with normal driving. The code it threw was related to under-boost, which the shop said was NOT common on the 4.0TT engine. The guys at the dealership had it for two days and had to open a case with Audi TAC to eventually track down the issue, which turned out to be a broken hose down deep on the side of the engine. (Not visible from the top).

In short, I had similar issues and it wasn't easy for a service tech with an excellent reputation to track down, even with TAC help. Now that the hose is replaced, the car runs like I would expect. Good luck!

[BlueSVT]

Had a buddy with a 335is that had a similar issue... and was a cracked turbo outlet hose, causing a boost leak. Surprisingly, you couldn't really hear it. Ran like new after it was fixed.

Hopefully its a minor issue!

[jb1970]

Still have not found what the issue is.

Thanks for all the suggestions so far.
Most of the replies seem to think a boost leak is the issue.
The repair shop initially hoped that was the issue, but since then the car has developed a problem with a rough idle.
I don't think this would be related to a boost leak, since the car is not trying to generate boost at idle.
So the priority is to fix the rough idle.
One idea was clogged cats, but apparently they checked and its not that.

This car is a former salvage (from minor water damage) and so does not have a warranty.
That was a big factor in why I did not hesitate to get the APR tune.
The APR dealer/repair shop is working with APR and trying to help me find/fix the problem (including ruling out the APR tune as the cause) but its a slow process.
At some point we may have to give up and just take it to a dealer.

[jfeger]

FYI. I had a. I had an instance of a rough idle with mine before I had the EPC light come on.

1: have you done multiple pedal to the floor tests, perhaps using straight on-ramps to highways?

2: during those tests, have you done your logging? There is a capture option with VCDS that shows actual vs specified boost pressure. That's a great tool.

3: Even without engine light or EPC, I had codes VCDS retrieved prior to the lights. That was related to misfire.

Your issue sounds VERY similar to mine. The lack of trouble lights was bizarre, but enough wide open throttle eventually tripped it.

PS - My issue is fresh, as it happened two/three weeks ago.

Sent from my iPhone using Tapatalk

[jb1970]

The car was perfect on Saturday night.
On Sunday morning it was very low on gas so I went out to fill up.
I was driving normally, listening to the radio.
Became aware of a whirring noise and a lack of power, turned off the radio to verify it was not that.
Could hear the whirring noise increase as I would accelerate.
I did not push it as it was making a noise.
Got to gas station and filled it up.
After about 1 or 2 miles I noticed the whirring noise had decreased/stopped.
But there was very little power even when I floored it. It would rev relatively slowly and accelerate moderately.
It would just about keep up with accelerating traffic under full throttle. Once traveling at speed it seemed normal enough.
So now there was no CEL and no rough idle.

On Tuesday morning I drove it 50 miles on the highway to the APR dealer.
As I got off the highway and waited at a traffic light I began to notice the idle get rough.
This continued to get worse while the dealer was checking it.
And thats where we are now.

It was not generating fault codes for the repair shop until they pushed it hard on the highway.
Now they are getting some codes, but not specific guidance on what may be wrong.

[tenspeed]

Update:
The car was flashed back to stock and still has the same problems.
Other than the car is running very rich, they are not getting many ideas as to what exactly is wrong yet.
Running rich and not generating boost, but don't know why.
Hopefully tomorrow will bring some clues.

Normal (non turbo) common causes for a rich mixture are bad intake air temperature sensor and bad O2 sensor. When all else fails, they might want to check them out.

[jb1970]

I'm pretty sure that the water damage was very minor, even though the car was salvaged. But I wouldn't rule it out completely either.
The carpet got wet, but I don't think water got in the engine/electronics.

The car has only 11k miles, with the tune on it since about 6k miles.
I don't avoid giving it WOT any chance I get, but the car has definitely not been abused.

[jfeger]

Post up the codes.

^^^^^ +1

As soon as I was able to get a code thrown, the shop was able to start tracking it down. Like I said, mine was translated as a direct under-boost condition.

[jb1970]

Was talking to the repair shop and they mentioned the following 2 codes:
P0175 System too rich, not confirmed
P0299 Boost regulation, not confirmed

[bhvrdr]

Still have not found what the issue is.

Thanks for all the suggestions so far.
Most of the replies seem to think a boost leak is the issue.
The repair shop initially hoped that was the issue, but since then the car has developed a problem with a rough idle.
I don't think this would be related to a boost leak, since the car is not trying to generate boost at idle.
So the priority is to fix the rough idle.
One idea was clogged cats, but apparently they checked and its not that.

This car is a former salvage (from minor water damage) and so does not have a warranty.
That was a big factor in why I did not hesitate to get the APR tune.
The APR dealer/repair shop is working with APR and trying to help me find/fix the problem (including ruling out the APR tune as the cause) but its a slow process.
At some point we may have to give up and just take it to a dealer.

Some things arent adding up and its likely (and hopefully) just information getting lost in translation going from your shop to you to us on the forum.

1. You have no/low boost and you have rich codes and underboost codes.


2. You took logs but they were bad logs and won't show any issues because they were part throttle driving. You still need to do take a proper datalog for diagnostic purposes.

3. Your shop supposedly does a boot leak test at 1psi. Either that was an error in translation or your shop made a mistake and needs to redo the boost leak test at 15psi.


According to what you have posted a proper diagnostic has not been performed yet on your car so its really hard to start ruling out the most obvious things before any of us start recommending the more rare things (ie, sure it could be a bad turbo, bad wastegates, bad N75 but not as likely).

I would get a good set of datalogs, get a good boost leak test and then post those results.

Mike

[jb1970]

I admit to knowing very little about this stuff, so I could be doing a bad job of reporting back.

The car is an hour away and I have not had a chance to retake a log, done properly this time.
The repair shop seems to be looking at blocks in a more targeted way, rather than the complete WOT log approach.
They are reporting back what APR is asking them to look at, but its a rather slow process.

I believe there is a difference between a traditional high pressure boost leak test (15psi) and a low pressure smoke leak test (perhaps at 1psi).
One or the other may be easier or more appropriate depending on the issue..


The repair shop is doing their best to come up with a diagnosis, at a reduced rate/for goodwill as long as I can be patient.
At some point we may both agree to give up and try the Audi dealer.
I don't know what attitude the Audi dealer will adopt to a non-warranty, tuned former flood car.

[jfeger]

Was talking to the repair shop and they mentioned the following 2 codes:
P0175 System too rich, not confirmed
P0299 Boost regulation, not confirmed

P0299 was the code I had. Mine was an under boost condition where "control range not reached". The system being rich would likely being an artifact of the lack of boost. I'd definitely focus on the under boost condition.


Sent from my iPhone using Tapatalk

[bhvrdr]

I admit to knowing very little about this stuff, so I could be doing a bad job of reporting back.

The car is an hour away and I have not had a chance to retake a log, done properly this time.
The repair shop seems to be looking at blocks in a more targeted way, rather than the complete WOT log approach.
They are reporting back what APR is asking them to look at, but its a rather slow process.

I believe there is a difference between a traditional high pressure boost leak test (15psi) and a low pressure smoke leak test (perhaps at 1psi).
One or the other may be easier or more appropriate depending on the issue..


The repair shop is doing their best to come up with a diagnosis, at a reduced rate/for goodwill as long as I can be patient.
At some point we may both agree to give up and try the Audi dealer.
I don't know what attitude the Audi dealer will adopt to a non-warranty, tuned former flood car.

I understand. It's a frustrating process for all i'm sure.

I didnt want to seem like i'm bashing you or your shop. They are likely racking their brains trying to find the leak and there are a lot of possible areas. They're going to need to keep checking every possible hose, every connection to boost solenoids, all vacuum lines, everything. They need to make sure the boost is leaking though to know it is a boost leak and a higher pressure test will tell them. If they cant get boost to leak then it may not be your reason for underboost. Im guessing it is just like they are but if the car holds 15psi without leak then its time to look else-where. 1psi of smoke may not be enough to get the leak to occur if its a partial or self sealing leak.

Mike

[jb1970]

I understand. It's a frustrating process for all i'm sure.

I didnt want to seem like i'm bashing you or your shop. They are likely racking their brains trying to find the leak and there are a lot of possible areas. They're going to need to keep checking every possible hose, every connection to boost solenoids, all vacuum lines, everything. They need to make sure the boost is leaking though to know it is a boost leak and a higher pressure test will tell them. If they cant get boost to leak then it may not be your reason for underboost. Im guessing it is just like they are but if the car holds 15psi without leak then its time to look else-where. 1psi of smoke may not be enough to get the leak to occur if its a partial or self sealing leak.

Mike

Certainly no perception of bashing here...and I appreciate all the feedback.

The repair shop is going to look into a few more things today and hopefully discover something.

[Sean@APR]

Was talking to the repair shop and they mentioned the following 2 codes:
P0175 System too rich, not confirmed
P0299 Boost regulation, not confirmed

99% sure this is a boost leak. Tell the shop they need to pressurize the system and it should be very obvious where the leak is after that.

[VVG]

99% sure this is a boost leak. Tell the shop they need to pressurize the system and it should be very obvious where the leak is after that.

Thanks for confirming the most likely culprit here. Is it correct to assume, then, that system is calling for fuel based on what it should be getting for manifold pressure based on throttle position. Since the boost isn't hitting spec, you will run rich??

[jb1970]

Will be dropping the car off at the Audi dealer first thing on Monday morning.
Lets hope they can get to the bottom of this quickly.

Still has the same problems: rough idle, slow to rev, poor acceleration.
It also now lets off a burst of gray smoke from tailpipes on startup.

[BlueSVT]

Hopefully the continued "testing" with issues hasn't created a bigger issue...

[Sean@APR]

It also now lets off a burst of gray smoke from tailpipes on startup.

What did it smell like?