Will an N75 Valve fix this? (codes inside)

[X-ZZ4]

My car is falling on it's face when I attempt to accelerate. If I feather the throttle.....it is drivable (barely), but there is no boost. But any normal acceleration, it falls on it's face, wants to die, and throws codes.

Here's the codes.....

#1 - 16490 - Manifold Pressure / Barometric Pressure Sensor (G71) / (F96), Implausible Signal
#2 - 17956 - Boost Pressure Regulation Valve (N75), Open Circuit
#3 - 16620 - Manifold Pressure / Boost Sensor (G31), Implausible Signal

I'm thinking for $100 I'll just try the N75. Any other suggestions?

[frankwizzle]

Don't just start throwing parts at it. Sounds like an issue with the map sensor or a severe leak, possibly from a torn tbb. What are your fuel trims?

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[X-ZZ4]

TBB is good. I've replaced damn near every hose I can find on the thing. The spider hose helped smooth the idle a ton....and it runs VERY smooth now. It just falls on it's face acceleration....and this just started.

Like I mentioned....I thought I had leaks, and I'd been putting off doing the spider. But I did it, and no change on the power issue.

I really don't mind spending $100. Eliminating that as a potential problem is worth $100 to me. I checked out the wires and connected lines last night again....all looks good.

So I'm buying the N75 today and I'll install tonight. We'll see.

But any other suggestions are appreciated as well. This car seems to require two or three attempts to fix anything.

Ok...it's not the car. It's me......I'm new at this Audi thing.....LOLZ

[X-ZZ4]

Got a chance to do the N75 this morning. Yep.....$100 down the drain. No change.....oh well....one more possibility eliminated....LOL

I did drive it a bit harder this morning. If I keep on it a bit after it recovers from falling on it's face......it will build boost above 3000 RPMs. Not smooth.....but it is definitely boosting. I didn't put a gauge on it, saw no purpose because I ain't staying on the throttle long running like this. But it felt like a decent amount of boost.....fairly normal.

Same codes. Suggestions?

[LakeTahoeQuattr]

I am 99% that it is a boost leak. Check all the pressure hoses. I had the exact same symptoms. I know you said the TBB is good, it is fully seated on the throttle body?

[X-ZZ4]

I am 99% that it is a boost leak. Check all the pressure hoses. I had the exact same symptoms. I know you said the TBB is good, it is fully seated on the throttle body?

I'll double check everything again, especially TBB. Who knows....maybe it's not fully seated.

It is running good enough now to where I just drove it to the office. Once it's above 2000 RPM it seems almost fine (not perfect.....but it feels pretty good). I'm thinking it just has to be vacuum/boost. The search continues. Maybe I need a smoke test.

[Kruat]

Any other symptoms when the problem occurs? Any loud noises coming from engine bay? Does it surge back and forth? It also sounds like a boost leak to me as well, although your getting implausible signal errors on your G71 and G31 sensor. I'd check all wiring, make sure there is no damaged wires to both of those sensors.

[X-ZZ4]

Help me out with the G71 and G31.

Where are those located? Any pics?

[frankwizzle]

I take it they don't have Google in your parts..G31 aka the map sensor is on top of the tbb.
G71 is in the ECU.

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[X-ZZ4]

I take it they don't have Google in your parts..G31 aka the map sensor is on top of the tbb.
G71 is in the ECU.

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Were you born a dick or was that a mod? Geez....first you TELL me not to throw money at it. As if you have insight into my budget or income.......LOL

Now smart ass remark about Google. Yet you still typed in the answer. Thanks. I guess.

[frankwizzle]

LOL, easily offended I take it.
I put abecause I was just teasing. No need for name calling, I'm trying to help ;p
I never said anything about money, I said not to just start throwing parts at it. Its best to figure out the problem and then address it. Fault codes don't always explicitly tell you what's wrong, you have to interpret them to figure out the issue (symptom/problem dogma).
Back to topic, CHECK YOUR FUEL TRIMS guy. That will help determine if you have a leak. After that we can look other possible issues.


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[X-ZZ4]

Speaking of touchy......geez. Your little emoji showed up as an X.....so sorry if I couldn't read your mind.

[frankwizzle]

Speaking of touchy......geez. Your little emoji showed up as an X.....so sorry if I couldn't read your mind.

colon P isn't an emoji. Post your fuel trims

[X-ZZ4]

Frankwizzle....

Sorry if we got off on the wrong foot. I apologize. Tough day at the office, and frustrated by these issues.

I'm on my phone now and can clearly see your smiley. It didn't show up on my work PC.

I'll see what I can do about those fuel trims. I'm also gonna do another exhaustive search for a leak or broken wires. And I called a shop in town and they'll do a leak test on it for $105. I'm gonna take another good look for leaks....I really feel this has got to be something stupid and easy. I just ain't finding it. But for $105....I may punt it to the shop and let them see if they can find a leak.

I'll take a look at the car again in a couple hours....or maybe tomorrow. This WILL get fixed one way or another.....lol

[frankwizzle]

It's all good man.
I need to apologize too as I'm on Eastern time and while you're halfway through your day I'm probably already deep into happy hour, so I may be asshole-like at times

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[LakeTahoeQuattr]

The symptom I experienced then my tbb was like 1cm away from my throttle body was that it would not raise the rpms over like 2000. The boot was not ripped but I was too blind to see that it was not fully seated on the throttle body.

Lets take a step back for a minute. If you are getting open circuit on the n75 and others then it MUST be the wiring harness or ecu correct?

Clear codes and they return?

[frankwizzle]

Disregard. See NTQs response

[X-ZZ4]

Update - FIXED!

It was the MAP sensor...just as called out in one of the codes. I was hesitant replacing it after missing on the N75, especially since the MAP is $230 locally, even $210 at ECS. But I found a used one on eBay for $60 (used oem Audi part from wrecking yard), said what the hell and took a shot.

It arrived today, I installed it in 10 minutes....reset codes...and WOO-HOO....runs awesome!

Thanks for the suggestions, input, and help to everyone!

[X-ZZ4]

So here's a bit more info for anyone who may find this thread in the future. And it also answers LakeTahoeQuattr's last question.

It initially set all three of the codes in my first post.

I replaced the N75, and reset codes. No change. As soon as I drove it all 3 codes reappeared.

I then replaced the MAP sensor (I had not reset codes). I started it up, went to clear codes, and noticed now there were only 2 codes. The N75 code was no longer set, it seems to have cleared itself. The two MAP codes were still there. I reset codes....took it for a test drive....And all is good. Took it for a longer drive....and all remains good. So unless it also needed that N75 valve (which I doubt), it appears this was the MAP sensor the whole time.

One of the reasons I think this was difficult for me was that this wasn't the only thing going on. I knew I also had intermittent but minor boost or vacuum leaks. And I had already purchased the spider hose and was waiting to install it. So when this issue started...I figured it was time to finally do the spider.

So I did the spider. When I was in there I noticed the secondary air injection "tube" also had a broken connector and was leaking. So I also picked up that tube and installed that. I was hoping these two parts would fix or at least help my immediate issue of the car falling on it's face. But it didn't.

Only then did I install the N75....And when no fix then, the MAP. So there were multiple things going on....multiple fixes taking place...and it was always in the back of my mind that I did something wrong on the spider install. But it was also in my mind that I'd been searching for and fixing leaks already....And I was fairly confident that I had found and fixed everything.

So there were mind games going on in my head the whole time too...lol. Glad it finally all came together though.