# Low MAF values, Low BOOST and no Power.



## jesusxd00 (Sep 10, 2021)

Hello. I have an Audi TT mk2 2.0 tfsi, secondh hand. 10.000km after purchase, i lost power suddenly one day. 
-I have 5psi fron 2500 to 4000rpms (Low)
-I have 45 g/s maximum in MAF (Very Low)

Things I changed:
-Diverter Valve
-Maf sensor

-Map sensor checked
-Throttle values are correct
-Fuel pressure values are correct

I pushed air through intake for checking boost leaks. Air was escaping through oil dipstick. I must change PCV valve. But i dont know if this is the problem of low air FLOW and no low BOOST. 

No errors. Only maf sensor error and low boost error if i push to 4000rpms (engine cannot push more)


Any ideas?


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## FNChaos (Nov 30, 2016)

Your PCV should have a one-way check valve to allow pressure from your crankcase to escape (not to enter).

Boost, MAF readings, etc are likely just symptoms, not the cause of your problem so I wouldn't get too caught up chasing those issues just yet.

There is a slight possibility that you could have engine piston ring damage (allowing air from your intake to slip past into your crankcase), but I wouldn't even consider going down that path until I replaced the PVC.


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## jesusxd00 (Sep 10, 2021)

FNChaos said:


> Your PCV should have a one-way check valve to allow pressure from your crankcase to escape (not to enter).
> 
> Boost, MAF readings, etc are likely just symptoms, not the cause of your problem so I wouldn't get too caught up chasing those issues just yet.
> 
> There is a slight possibility that you could have engine piston ring damage (allowing air from your intake to slip past into your crankcase), but I wouldn't even consider going down that path until I replaced the PVC.




Hello. Thanks for your answer. My question is, can a faulty PVC provoke enough boost leak to be running at 5psi maximum? As I say, car runs perfect, but its like having only 60 horsepower.


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## Hoggy (May 8, 2002)

Hi, Low boost could be a faulty N75 solenoid valve.
Hoggy.


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## FNChaos (Nov 30, 2016)

A faulty PVC (or any boost leak for that matter) can cause your car to go into '_limp_' mode, causing a reduction in power. However, If this were the case I would expect a CEL to be illuminated on your gauge cluster.

As Hoggy suggests, your N75 can definitely cause boost leaks but that wouldn't explain your leakdown test results.

Still, PVC valves are high-failure items that are easy to replace. I'd suggest its the best (and cheapest) place to start.


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## jesusxd00 (Sep 10, 2021)

Hoggy said:


> Hi, Low boost could be a faulty N75 solenoid valve.
> Hoggy.


Hey! I think mk2 2.0 tfsi engines dont have n75 valve. Its called diverter valve. I had it replaced.


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## jesusxd00 (Sep 10, 2021)

FNChaos said:


> A faulty PVC (or any boost leak for that matter) can cause your car to go into '_limp_' mode, causing a reduction in power. However, If this were the case I would expect a CEL to be illuminated on your gauge cluster.
> 
> As Hoggy suggests, your N75 can definitely cause boost leaks but that wouldn't explain your leakdown test results.
> 
> Still, PVC valves are high-failure items that are easy to replace. I'd suggest its the best (and cheapest) place to start.


Yes, i feel that maybe car is in limp mode. I can use only 1/4 of throttle, other 3/4 makes nothing. But i connected the car to vcds and i have no errors reffering to limp mode.


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## FNChaos (Nov 30, 2016)

jesusxd00 said:


> Hey! I think mk2 2.0 tfsi engines dont have n75 valve. Its called diverter valve. I had it replaced.


Your N75, aka your waste gate frequency control valve controls your waste gate actuator (mounted directly on your turbo) to limit the amount of pressure your turbo is allowed to produce. Your diverter valve is a separate device. It's purpose is to temporarily release boost pressure when your throttle suddenly closes (like when you let off between shifts) to avoid back pressure induced turbo flutter / turbo stall.

Note: A diverter valve and a 'blow-off valve are basically the same thing except a diverter valve diverts air back into your intake tract (since the MAF has already accounted for it) whereas a blow-off valve releases pressure into the atmosphere.


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## jesusxd00 (Sep 10, 2021)

FNChaos said:


> Your N75, aka your waste gate frequency control valve controls your waste gate actuator (mounted directly on your turbo) to limit the amount of pressure your turbo is allowed to produce. Your diverter valve is a separate device. It's purpose is to temporarily release boost pressure when your throttle suddenly closes (like when you let off between shifts) to avoid back pressure induced turbo flutter / turbo stall.
> 
> Note: A diverter valve and a 'blow-off valve are basically the same thing except a diverter valve diverts air back into your intake tract (since the MAF has already accounted for it) whereas a blow-off valve releases pressure into the atmosphere.


Hello,

I dont find any info of N75 valve related to 2.0 tfsi engines (audi tt mk2 8j). Please, could you share some info? Thanks.


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## FNChaos (Nov 30, 2016)

jesusxd00 said:


> I dont find any info of N75 valve related to 2.0 tfsi engines (audi tt mk2 8j). Please, could you share some info? Thanks.


The N75 is shown as Item 1. Depending on your motor, the recirc valve can be mounted up front (item 17 in the first pic) or on the turbo (item 3 in the second)


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## jesusxd00 (Sep 10, 2021)

FNChaos said:


> The N75 is shown as Item 1. Depending on your motor, the recirc valve can be mounted up front (item 17 in the first pic) or on the turbo (item 3 in the second)
> 
> View attachment 477862
> 
> ...


Thanks! So how can I check if I have a bad n75 valve? Which connection should I disconnect? I see lot of info about audi tt mk1 1.8t, but not about audi tt mk2 2.0 tfsi and n75.


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## Hoggy (May 8, 2002)

Hi, The N75 resistance on the 1.8T is 25-35 Ohms & probably the same on the MK2.
Hoggy.


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## jesusxd00 (Sep 10, 2021)

Hoggy said:


> Hi, The N75 resistance on the 1.8T is 25-35 Ohms & probably the same on the MK2.
> Hoggy.


Thanks. And if I disconnect the connector of this valve, will boost pressure return again?


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## FNChaos (Nov 30, 2016)




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## Hoggy (May 8, 2002)

jesusxd00 said:


> Thanks. And if I disconnect the connector of this valve, will boost pressure return again?


Hi,No it will default to 6 psi ish.
Hoggy.


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## Wolvez (Jun 22, 2018)

It's probably something mechanical. Convert the boost sensor reading @ hot idle to inch of mercury. Does the engine pull atleast 19 inches of mercury @ hot idle? If YES, the wastegate is probably stuck open. If NO, it's a timing issue.


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## jesusxd00 (Sep 10, 2021)

Wolvez said:


> It's probably something mechanical. Convert the boost sensor reading @ hot idle to inch of mercury. Does the engine pull atleast 19 inches of mercury @ hot idle? If YES, the wastegate is probably stuck open. If NO, it's a timing issue.


Hello. My turbo pressure at warm iddle is -22 Hg. So i have a bad n75 valve? I am monitoring my boost in wot and is near to 0psi. When i change gears, it drops to -22 Hg.

Thanks


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## jesusxd00 (Sep 10, 2021)

I am also noticing that I only have 1/4 of throttle usable. Other 3/4 throttle makes nothing


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## Hoggy (May 8, 2002)

Hi, No such thing as turbo press at idle, but with -22 @ idle you don't appear to have any leaks.
Have you checked the resistance or replaced the N75 
Hoggy.


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## jesusxd00 (Sep 10, 2021)

Hoggy said:


> Hi, No such thing as turbo press at idle, but with -22 @ idle you don't appear to have any leaks.
> Have you checked the resistance or replaced the N75
> Hoggy.


For me is verry dificult to acces to n75 in my audi tt mk2 engine. Today I will replace PCV, and I will try to disconnect one n75 hose, so the turbo wastegate will not open. If car has turbo again, is n75 and i will replace it at mechanic.


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## Wolvez (Jun 22, 2018)

MAF reading @ hot idle should be around 2-5 g/s. 

Have you tried running N75 output test using vcds? You need to remove the plastic fender cover to gaon access. It's nof accessible under the car.


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## TT'sRevenge (Feb 28, 2021)

A little late to the thread and most has been mentioned already....

There is indeed an N75, on both the EA113 and EA888 engines...the engines in these (Mk2, 2.0T) cars, all use very similar turbos. BW K03 on the standard output EA113, K04 on the HO EA113 (TT-S), and the EA888 Gen1/2 use the IHI JH5 (which is a K03 equivalent).

Note: The Gen3 EA888s (in Mk3 TTs and other MQB cars) employ a fully electronic wastegate controller--i.e. they don't use a mechanical pressure-actuated diaphragm. Fully electronic may sound better but these have a host of other issues and are more typically expensive to address, but I won't get into those since they're not really relevant to Mk2s.

The Mk2 2.0T wastegates are boost actuated and use the N75 to control whether the boost is recirculated into the intake side of the turbo (which will keep the wastegate closed) or whether it pressurises the diaphragm, causing the wastegate to open. The N75 is switched at frequency and is very fast to react, relatively speaking. The more common failure state of the N75 should be the non-energised state which would simply always route boost pressure directly to the diaphragm which would start to open the wastegate at the "cracking pressure" which is 4-5psi IIRC, as pressure increases the wastegate will open farther, being fully open somewhere around 10psi (again if memory serves).

As a note the factory (i.e. non-tuned) boost limit on K03/JH5 engines should be 11.5 psi; on factory-K04 engines (TT-S) it is 17.x psi. This is the kind of boost you _should_ be seeing if everything is ok.

N75s can fail but they're not a hugely common failure point I don't think.

Since it seems like you're getting no boost pressure at all (well first you say 5psi, the you say 0psi so I'm not sure), I'd hazard a guess that the N75 is probably not the issue because you should get some boost. It's either a wastegate stuck totally open or perhaps the turbo is done for and seized, or even something like a damaged/plugged cat or exhaust system


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## FNChaos (Nov 30, 2016)

jesusxd00 said:


> Hello. I have an Audi TT mk2 2.0 tfsi, secondh hand. 10.000km after purchase, i lost power suddenly one day.
> -I have 5psi fron 2500 to 4000rpms (Low)
> -I have 45 g/s maximum in MAF (Very Low)
> 
> ...


Going back to review your first post. Still sounds to me like your car is in limp mode.

Limp mode will limit your RPM's to ~4000
Limp mode will cut boost. Limit < 5psi
Limp mode will reduce throttle response and limit max speed

You said there were no errors. What are you using to check this with? If you are using a generic OBDII reader a lot of errors will go unreported. If you aren't using a VAG specific reader (i.e (VCDS, VAG401, OBDEleven) you can't do any real troubleshooting.


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## TT'sRevenge (Feb 28, 2021)

FNChaos said:


> Going back to review your first post. Still sounds to me like your car is in limp mode.
> 
> Limp mode will limit your RPM's to ~4000
> Limp mode will cut boost. Limit < 5psi
> ...


It's a good point because it could well be an electronic limiting rather than a mechanical one but needs to be properly troubleshooted as mentioned.


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## jesusxd00 (Sep 10, 2021)

FNChaos said:


> Going back to review your first post. Still sounds to me like your car is in limp mode.
> 
> Limp mode will limit your RPM's to ~4000
> Limp mode will cut boost. Limit < 5psi
> ...


Hello. I scanned the car and it showed me Underboost p0299


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## jesusxd00 (Sep 10, 2021)

TT'sRevenge said:


> It's a good point because it could well be an electronic limiting rather than a mechanical one but needs to be properly troubleshooted as mentioned.


VCDS cable is arriving by monday. What should I test and how?


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## TT'sRevenge (Feb 28, 2021)

jesusxd00 said:


> VCDS cable is arriving by monday. What should I test and how?


Well when you do a full scan you're going to see all the codes set both generic OBD-II and VAG-specific codes. You can see if there are any set that are indicative of limp-mode. To get out of limp mode you can simply clear the codes. I don't typically recommend "clearing codes" to try to fix something but it will take you out of limp mode at least until whatever set it into it occurs again. This is of course assuming the car is even in that state (it may not be).


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## jesusxd00 (Sep 10, 2021)

Wolvez said:


> MAF reading @ hot idle should be around 2-5 g/s.
> 
> Have you tried running N75 output test using vcds? You need to remove the plastic fender cover to gaon access. It's nof accessible under the car.


At iddle I have 3-4g/s. At WOT (very slow) I have maximum 45 g/s. 

I will connect VCDS tomorrow and check N75. As I see, if valve turns open and closed, and pressure doesnt change, I have a bad N75, right?


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## jesusxd00 (Sep 10, 2021)

TT'sRevenge said:


> Well when you do a full scan you're going to see all the codes set both generic OBD-II and VAG-specific codes. You can see if there are any set that are indicative of limp-mode. To get out of limp mode you can simply clear the codes. I don't typically recommend "clearing codes" to try to fix something but it will take you out of limp mode at least until whatever set it into it occurs again. This is of course assuming the car is even in that state (it may not be).


I have cleared codes last week in a mechanic with the typical obd2 machine. Nothing changed. Can be with my vcds cable another different result?


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## jesusxd00 (Sep 10, 2021)

FNChaos said:


> Going back to review your first post. Still sounds to me like your car is in limp mode.
> 
> Limp mode will limit your RPM's to ~4000
> Limp mode will cut boost. Limit < 5psi
> ...


I have used a generic ob2 reader. Tomorrow I will use a VCDS cable.

I am also experiencing a very low fuel consume. When car was running right, I needed 1 fuel tank per week. Now, with this "state" of my car, I use 1 fuel tank per 2 weeks.


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## jesusxd00 (Sep 10, 2021)

TT'sRevenge said:


> A little late to the thread and most has been mentioned already....
> 
> There is indeed an N75, on both the EA113 and EA888 engines...the engines in these (Mk2, 2.0T) cars, all use very similar turbos. BW K03 on the standard output EA113, K04 on the HO EA113 (TT-S), and the EA888 Gen1/2 use the IHI JH5 (which is a K03 equivalent).
> 
> ...


Thanks for your explanation. I will be testing tomorrow VCDS cable. I dont know right now my turbo pressure, as I am using a tricky obd adapter. But i have no power, very linear, only 1/4 of throttle useable, very low fuel consumption and 45 g/s at WOT. Car is running fine at iddle, and no strange sounds. The 2 codes I have is p0101 and p0299


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## TT'sRevenge (Feb 28, 2021)

jesusxd00 said:


> Thanks for your explanation. I will be testing tomorrow VCDS cable. I dont know right now my turbo pressure, as I am using a tricky obd adapter. But i have no power, very linear, only 1/4 of throttle useable, very low fuel consumption and 45 g/s at WOT. Car is running fine at iddle, and no strange sounds. The 2 codes I have is p0101 and p0299


Another thing to try is unplug the MAF, run the car without it, see what happens. But yeah before doing that let's see what a full scan with VCDS reveals...


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## jesusxd00 (Sep 10, 2021)

TT'sRevenge said:


> Another thing to try is unplug the MAF, run the car without it, see what happens. But yeah before doing that let's see what a full scan with VCDS reveals...


I did that. Engine light appeared and nothing changed. Same with map.


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## cb4 (Oct 26, 2021)

Take a look at this video


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## jesusxd00 (Sep 10, 2021)

This are the results from VCDS scan. Requested boost vs actual boost


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## jesusxd00 (Sep 10, 2021)

I checked the n75 with motor off and I hear a "click" so I think its working well. Maybe the cause of no boost is a broken diaphragm?


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## jesusxd00 (Sep 10, 2021)

FNChaos said:


> The N75 is shown as Item 1. Depending on your motor, the recirc valve can be mounted up front (item 17 in the first pic) or on the turbo (item 3 in the second)
> 
> View attachment 477862
> 
> ...



Hello. After a lot of information I think that the hose that goes into N75 maybe is bad. From where does this hose come? Thanks.


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## FNChaos (Nov 30, 2016)

jesusxd00 said:


> Hello. After a lot of information I think that the hose that goes into N75 maybe is bad. From where does this hose come?


Watch the video posted earlier. Hose connections described around the 2 minute point





Have you replaced your PCV valve yet? Also what error codes come up now that you have VCDS?


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## jesusxd00 (Sep 10, 2021)

FNChaos said:


> Watch the video posted earlier. Hose connections described around the 2 minute point
> 
> 
> 
> ...


I have replaced my pcv. When I installed the new one, idle was very rough. So i think the new one is bad, they will send me another one.

With vag com I only had 1 error, P0299. But this error only happens if I am 5 seconds in underboost condition (for example, wot). If I drive normally, no errors.

I tested n75 with engine off, and it sounds "click". My suspect is that maybe the hose that goes into n75 is broken, so there is no air/vacuum going to n75, and the turbo stick is no moving = open wastegate = no turbo pressure.

Tomorrow i will instal a camera (i cannot see it) to see if the waste gate from turbo is working or not. If it is not working, i will have to inspect the hose that goes into n75. If it is working... I will have to inspect the turbo.


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## jesusxd00 (Sep 10, 2021)

Update: I recorded wastegate during throttle and it doesnt move. It seems to be open. Tomorrow I will go to mechanic.


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## jesusxd00 (Sep 10, 2021)

Update: internal wastegate is working correctly. We think maybe I have a bad turbo, or a clogged cat. What do you think?


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## jesusxd00 (Sep 10, 2021)

Last update: turbo blades were stuck in turbo. Thanks to all


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