VW / Audi 2.0L Turbo - System Too Lean Diagnosis & Repair P0171, P2177 

Mike -- This was a very informative and revealing case study video on a lean operating condition and fuel trim data. I now know to consider several other sources of vacuum leaks besides manifold gaskets. One needs to keep in mind any device in or attached to the intake manifold that uses vacuum: EVAP systems, power brake booster, HVAC controls, etc. I know I will definitely keep these possibilities in mind. At time interval 49:30 you made my day when you pinpointed the EVAP purge solenoid as an intake vacuum leak source. You decided to plug its port and then retest to confirm your diagnosis. This simple tests takes very little extra time and does not involve extra expense. In that manner you have additional assurance that you are diagnosing correctly and "not firing the parts cannon" to fix a problem. Your discovery of a vacuum leak through the power brake booster but only when actuated was astounding. It proves that elusive vacuum leaks requires one to think "outside the box" and really understand how various systems on a modern automobile function and interact. If you decide to dissect that vacuum booster I am thinking that you will find that the internal valve that regulates vacuum between the front and rear chambers of the booster housing is leaking when the push rod is actuated. It is also possible that there is a small hole or tear in the diaphragm membrane.

Man! You are a life saver! Seriously I am dealing with this for 2 weeks now 😄 Its true that the biggest vacum place in the car, gets overlooked!

Finally this issue has been explained in a simple manner. I've been chasing a leak in my GTI with the same engine and haven't found anyone explain it the way you did. Thanks for this and I did subscribe and like this! Thanks man, take care

Your content is always excellent. Thanks for all your hard work and sharing your experiences with us!

Your very good young man. You let nothing distract you from completing the video. Your a natural! 👊🏿

Mike I usually like ur vids even before I watch them, And this one is no exception..... Thanks alot.

Just want to say thank you for this video. I found the issue with my 2.0 jetta GLI. Thank you.

Very detailed , gave me a huge amount of insight to diagnose this common problem on Audi vehicles.

The secret with the electrical connectors is to push and hold them in first, Then you can pull the tab down with your fingers. I used a screwdriver like you did for years then someone showed me the push in part. What a relief from that moment on😆

this is an incredibly helpful and insightful video! Thank you so much for making it!!!

Great video! Just as a heads up. When u want to convert the units of measurement, for example MAF to gr/s u can do it on the scanner instead of googling. With the PID showing u can hit the little drop down arrow where the graphing option is present and it’ll have an icon of a scale further right and that option switches the unit of measurement from lbs to grams. Thanks again for the class

Great video Mike! It’s definitely among one of the best case studies I’ve seen on Wells garage! 👍👍👍 You kept your cool and even though it took longer,we all learned a very valuable lesson when dealing with these cars! Next time a garage crosses their hands and ships it,you will be making “ quick money “ because you will jump straight to the issue! The fundamentals are pretty much the same,even when dealing with Euro cars and learning how they operate can only make one a better technician. I simply love the Autel,especially when it comes to these vehicles. Many scan tools have nothing on Autel. I have never dealt with Launch but I take your word on it! Thanks Mike!

Great video. My first time watching one of your videos and it’s seems like you guys are great techs. Keep up the good work.

The way to get VW/Audi connectors is push the clip, push the plug forward then pull out while still holding the clip 😋 Excellent tutorial btw, I took a lot out of this.

The world appreciates your knowledge💯... what you study I wanna follow ....

I have an Audi A3 2007 and this is spot on. My car was not holding boost at all . It was giving lean problems etc. I cleaned the maf and my car run better but still not holding boots ,turns out my brake booster lines were cracked and my oil dipstick melted. I haven’t checked the solenoid yet but I tapped the brake booster and did a pull and it was now holding boost. At 10 psi. I tapped the oil dipstick and it went to 17 steady. But I did get the engine light code again. I’m ordering the proper parts now and hopefully it completely fixes the issue

Excellent video Mike! Glad I found it. Trying to identify what is causing my Seat Leon 1,8 tsi to have a P0171 and you gave me excellent material to search! Best ragards from Athens Greece!

What a fantastic course this was! Thanks for the instruction Mike.

You can always change English to Metric measurements with your scan tool to check the maf by going to the bottom of the scan tool and you where it shows M click on that and go to a settings that way so you don’t have to exit out to get there... I was stoked when i discovered that!

You’re brilliant man. I actually have the same engine.

Definitely a good and informative video. I’ve got an 11 Audi A4 2.0 at the shop with the system lean at idle and it’s been racking my brain as I normally don’t work on Audis either but i think this is definitely gonna help me in the right direction. Always nice to learn something new. Thanks for the info.

Speaking of leaving these timing chain type engines specifically VAG, parked on a hill in gear, I've had quite a few of these manual transmission cars left on a hill for example 1st gear facing up hill where they've rolled backwards slightly, turned the engine backwards and jumped the chain. The owner has then started the engine and mashed the valves. I Always advise if leaving in gear, 1st gear facing downhill, reverse facing uphill so if the engine is turned by the weight of the car, it's turned in the correct direction. Great informative video also. I got the brake booster answer straight away too!

I'm so happy you chose this engine please more videos

Excellent video, Keep up the great work!! My 2008 Audi with the 2.0 FSI engine does not use manifold vacuum for the brake booster, It has a separate vacuum pump for the brakes. I have replaced both o2 sensors, the pcv and maf sensor. I think my issue is the solenoid purge valve. BTW I have 225,000 miles on it. THANKS!!!

Nice find.I have often looked at fuel trims when clamping the booster hoses. I have never looked at fuel trims while pressing the brakes. With Germany cars I use obd 2 data.

Great Diagnosis. You remind me of Scanner Danner. Great job. Also heating A/C system sometimes uses vacuum.

Mike, great and enjoyable video full of lots info thanks for sharing. My answer is D) neither.

Great case study! Great find!

Awesome class I missed it by an hour.

Amazing video very knowledgeable.. Thank you

Mike thanks for the reply.

Do vacuum leaks on turbocharged engines behave different than in NA engines? Eg when you rev the engine a vacuum leak could make iteself not noticeable compared to the amount of air entering the system.

Very informative , thank you!

You're amazing! You've helped me being a female working on my VW. Thanks

Wow. Excellent Analysis. Thanks!

I have been going in circles with a lean code on my 09 VW with a 2.0 tsi. Watching this video the light bulb went off, when I depress my brake pedal my RPM jumps around. I know what I will be checking tomorrow. I would not have thought of this in all of my years of experience...damn Germans.

Great video! Its 5 years old but still very informative. I have the "system running lean at idle" code on my A4 B7 2.0TFSI. 174500 miles, recently stage 2 tuned. About 8 weeks ago, now getting this lean code and misfires when I put my foot down and the car is stuttering and I just lift off. Changed spark plugs, still stutters when trying to accelerate hard. Changed the spark plugs back, changed the coils, same problem. I also cleaned the MAF and it did improve, but started to splutter again. Put my newer coils back on and not really sure what the issue is now. It runs perfectly under normal driving, its only an issue when you suddenly floor it. First symptoms/signs of an issue was a code saying "Pressure in fuel rail too low". So my friend fitted a HPFP upgrade internal piston (really needed for stage 2 cars). Still have the issue. I have a brand new LOW pressure fuel pump for an RS3 (should be a direct swap for my car) so im going to fit that on Saturday and I hope that is my issue. OBD 11 showed at idle my 1/2 pump is 58.8% and when I floor it It jumps to about 76% and then it misfires. If I stay on it, It will give me a code for cylinder 2 misfire and random multiple misfires. The intake valves were recently cleaned and cam chain and belt have also recently been changed prior to any issues. If this pump doesn't fix it im taking it to a shop and paying them to sort it...if they can. If it were coils or spark plugs, wouldn't the misfire be constant and not only when I floor it?

Good morning Mike. I always enjoy your great videos. Perhaps a suggestion. For us old guys, and for young ones too. Scan tools and scopes become popular pretty much after points went out. But points and condenser were able to do electromechanicaly what transistors do invisibly. So if u were to do a class that brought in an old car and u did your magic, imagine how much better us old knuckle draggers could get it. If using the Pico the channel connections could b as follows. 1. B+ 2. Negative side of coil 3. Point side of resistor. 4. An amprobe around the supply wire. As the engine is running, or the distributor is turning the dwell as expressed in degrees of rotation would remain stable at about 30(v8)degrees. But the square wave, or ? Would change with rpm. That would help us to comprehend the time base function of the scope. The resistance of the resistor varies with the time that it is on, as in points closed ignition on. Remember when people would listen to the radios and burn up the points? Trained by Techs did a great video on a fuel pump actually running in a tub of water, as u have done with tanks and evap situations. Videos which were very instructive. Anyhow, just a thought. U have the facilities and the subs to best present that. And, u CAN wrench. I remember the Toyota video where u turned nuts and bolts. Thank u!!

muy buena leccion me gusto mucho..eres un genio..muchas gracias..amigo!

Great class!! It would have been interesting to look at global obd before you cleared the codes. At least just for the fuel trim pids. Values cannot be substituted under global obd and if the vehicle is running lean, that’s what you will see...

VERY GOOD DIAGNOSTIC SKILLS GUYS

This was great Mike. I would have liked to see the OBDII data on the fuel trims. It might have made it make a bit more sense.

Good video n explanation thanks. 👌

one tip for any of those connectors to pop off is to actually push them in slightly as you are lightly pressing the tab with the screwdriver and then you can pull them off hopefully without breaking them as they get brittle.

Hey, very informative thank you.Do you have a video covering p0089 code for Audi A4 2.0. I have a b7.

super helpful, thank you!

EXCELLENT TURORIAL VIDEO IT WILL SAVE A LOT OF MONEY. CHEERS AND MAKE MORE VIDEO IN AUDI A4

Could u have watched fuel trim on obd2 ? After all, the fuel trim was the biggest clue. We r also much more familiar with those readings. Really great session!!

Amazing video bro thanks

Hey, Mike. I was wondering if you wouldn't be able to differentiate a pcv valve, an egr valve, a purge valve lean conditions by symptoms. I would think that a purge valve lean condition would make the vehicle runs rough as well as an egr valve. Your thoughts on that?

Hey, Mike. Have you ever repeatedly pumped the brake pedal to drive the o2s lean instead of disconnecting a vacuum hose? I learned that from a tech, but can't get to figure out how that happen. I read a lot and asked around trying to figure it out. I am always told it i a bad booster, which is not. I do that on multiple cars and all of their 02s go lean. The check valve should not allowed vacuum into the intake. How that happens? It may remain a mystery for me.

used to hear them hissing inside the vehicle with everything closed and fan off, but newer cars usually have panels and insulation dampening the noise. one of the diagnostic steps should always be applying and holding the brakes while watching data, you just never know, been bitten before on older cars. live data would have been nice then! I've replaced quite a few leaking units, all 90's and older though. most were bad/dirty valving inside and pulling through the pedal shaft area and hissed fairly loud.

hey there.....I have the pcv valve issue.....lean bank one and a loping up to 2000 rpm continuous issue. Cannot get the valve cover cap off while running. Is there a way to defeat the valve for now. Only source for this pcv valve I can fine is ebay.....so 7 days out and I do not want to blow my engine seal....can we pull a hose and just plug it ?

Hey Mike. Damn I missed the livestream. This is another awesome presentation. Had new carpet being laid. Man you are good and thorough. I made a paint can smoker and i like the fact that it will blow the lid off like your yellow plastic caps did if too much pressure. Won't break any components. Also I've had to replace the brake booster vacuum check valve more than once on F150's. I've never thought to check the booster internal diaphram but now I'm more aware. Whats your total time invested in this one? LOTS!! Thanks Mike.

Great video Mike. I think i have air issue in my 2.0 tfsi mk5 gti. When i try to remove the oil cup in my car there is huge and the car run very bad at idle it shakes a lot sometimes the engine turn off. So i bought a new pcv valve, and the same problem again. Do you think there is any ather problem than pcv, or the new pcv is bad again since in my in my country most of the parts came from china?

NICE ... that was killer dude

Great video, my friend has a 2009 VW GTI 2.0 TSI engine. It just threw codes P0171 and P0507. There is no vacuum at the dip stick, oil filler cap or at the small hole on the diaphragm housing. When I remove the oil cap I get air coming out. Could this still be a bad PCV?

Money is tight what is an affordable scanner with bi directional control mainly for evap troubleshootig open and close various solenoids while using smoke machine. Im looking at the autel 808

great video Mike thanks

Very good information

Thank you, Mike. I, now, understand how you can get a lean condition from a brake booster. How would you explain a lean condition when you keep pumping the brake with a good booster? I am thinking that vacuum on the other side of the booster is pushed back into the intake manifold.

hope i fix my Audi- brilliantly explained

I work on VW, Audi, Seat and Skoda (all the same group) quite often. To get those connectors apart PUSH the connector closed and whilst holding connectors together pull the tab then pull connectors apart whilst holding the tab back. P.s. Can I have t-shirt and hat? 😁

on a 02 1.8t would be a common as well? i got the code for the emissions and here in cali they are very delicate. I plugged a smoke machine as well and no air coming besides the airfilter unit but i did have an issue when the radiator top hose blew and replaced it. I cant seem to find the issue for this.

Great vid. Could someone assist with an issue on my 2015 Audi A5 2.0T? It's bone stock. I have +20 to 25 percent LTFT trims at idle. STFT stays at 0 after ltfts take over. No codes!! I smoke test and corrected leak at turbo inlet pipe and oil stick. Helped a little but still running lean. Cleaned MAF, no change. Replaced pcv with new oem, no big change. Fuel pressures look just fine. I haven't done anything to the injectors but no evidence that they are bad. Car has no symptoms, no misfires.

what are the symptoms of a bad brake booster? i have an 04 camry with 200k on it and i think the brake booster is going on it . lmk . thank you

Hi Nice video buddy, i've found my brake booster hose cracked could it be the issue for my.p0171 lean condition ? Causing little missfires also

Mike your great brother keep it up.

My tsx got 2 codes p0171 and p0134 dose that mean i just need to replace the o2 sensor?

Who do you recommend (a evap tech) in las vegas. I havehigh tank pressure and vapor relieving through fuel cap. Replaced, fuel cap with oem, fuel shut off, vent, purge, canister and filler neck. Fuel pump with internal rov/orvr seems ok. Cleaned tank. 80k miles

Will a stuck open pcv cause a lean condition even if the air its drawing in is metered?

Thanks Mike Good Imformation ++++++++++++

On ya mate awesome work !!

Hey Mike, when are you going to put on some more technical videos? I need some more t-shirts! LOL

This vehicle uses a vacuum pump though. Doesn't brake booster vacuum come not from the intake but the mechanical vacuum pump and electric pump?

Hello, I want to thank you for your video, it really helped me a lot to understand the vacuum system and how it can cause code failures, I have fault code 00561 - Mixture Adaptation: Adaptation Limit (Add) Exceeded in my audi A4 1.8T 1997, I already exchanged some parts, and did some tests, but I still couldn't solve it, I still don't understand if it is a "rich" or "leak" fault code or how to solve it, I have the fuel pressure in idle mode at 4 bars, I think it's too high, is it? the values of my trims are: 5.5 in (add) and -4.7 in (mul), thanks for everything

Hey man nice video! Can you help me? My car has this fault codes P2177, P1093 and P119A (Sensor G247 Malfunction).. Boost pressure, rail pressure, MAF are ok. When I clear the codes, partial Self Adaptation goes to 0%, but when I start driving it keeps rising until 25% and then all cylinders timing retardation goes to -12º KW, have you ever seen something like this?

Great video Mike. Tech A is wrong. Going with B

Good job, thanks

I have same engine running lean. Did smoke test, purge solenoid test, new maf and lambda even injectors tested and ok. Only thing I found is the brake booster trick when pumping stft goes up to 25. But will it make the engine lean even when not pressing pedal? Cold loop idle is rough. Reseting trims makes stft +25% and overtime ecu corrects it as ltft idle +6.5% and when driveing ltft undeload quickly goes up to +20%. So could it be brake booster or is there anything else I could check.

Just wondering 🤔 how brake booster works with a turbo? It builds positive pressure in manifold, meaning it is not draining vacuum inside booster, but how you still able to brake properly?

drain backing up, lol. I was expecting screaming and running away from it as brown floaties came forth.

Good class.

Hey. I got a wrx sti that is setting a lean code. My long term fuel trims are 24%. Short term is 3%. I home made smoke tested the vacuum system and found a leak and fixed it. But I’m still seeing same number after Ecu reset. When I did the smoke test I took oil cap off and smoke is coming out of oil fill. Is that normal?... what would you suggest? I already changed out maf sensor. And front 02. I saw that you said smoke out the oil fill could be an issue but do you have specifics for an sti 2013

i recently replaced a brake booster on a 2011 altima.the booster itself its from nissan dealership.after i replaced it, two days later p0171 code showed up. i already smoked the intake for leak.nothing found. check maf sensor operation.seems okay. am i suspecting a faulty oem brake booster from nissan. what steps would you do next? i havent check the fuel pressure,because the car seems to run fine.

My Audi A4 2009 2.0 TFSI (automatic) has this P2177 lean code. I did notice that sometime my brake pedal will be rock hard. Do you think my brake booster is the source of vacuum leak that causes the lean off idle issue? Please do get back to me as soon as you can. Thank you!

but this car has a vacuum pump for break boost. how can it possible for it to produce a leak?

If you would have had a leaking brake booster wouldn't you have felt the brake pedal going down at a stop when you were on your test drive? Did you even take it on a test drive?

Vcds will show you everything on VW and audi

What the part number of the brake booster thanks ?

I have jetta 4 1.8 turbo but it did mixed petrol an oil in the sum of engine.

A word of wisdom for those of you looking to dabble with European cars. This is all I do, this is all I know. Autel, Launch, sure good coverage, competitively priced, good compatibility, until they don't. Until you start chasing false codes. Until you run bidirectional tests and they don't work properly. Until you clear adaptations and corrupt module programming... If you want to reach professional level coverage on a Euro car, you need a Euro dedicated scantool. That means OEM, or maybe an Autologic.

I have the code p2177 on a 2014 Passat, the car doesnt run rough but that code won’t go away, what’s the first thing I should replace ? Thank you

Hablo español.. pero entendi todo!! Por esa maldita membrana del brake booster.. tengo un error p0171 en un audi a3 1.6 2008 manual BSE motor

Did he ever show the inside of the brake booster?

I first got code P12A2. The next day, I got an extra code P0171. We did a smoke test, no leak. We don't believe it's the high pressure fuel pump or fuel sensor, we might be wrong. 🤷‍♂️ We strongly believe it's a leak somewhere, but we can't find it. Any suggestions?

DC has it, push connector in, push tab, pull off.

Is the pcv closed during idle?

How many hours do you have into the diagnosis?

What about that check valve that only allows vacuum to the booster