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GLK x204 3.0 V6 4matic
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Discussion Starter · #1 ·
Hi Guys,

I'm new here - I have MB GLK x204, year 2010 with petrol engine 3.0 V6 (272.948).

I got two errors from ECU today (with check engine light) - system too lean (bank 1 & 2) (P0171/P0174 - 0745/0749)

I popped the hood and there was a noisy sound of leaking air (pressure), which came from the back side of the engine. Then I put off the plastic covers of the engine and noticed that this sound came from around of flowmeter (but not from the flowmeter itself). Then I realized also that the engine rpm increased themselves, without touching the accelerator).

Do you knowe from where this leak could come from and what I should do next?

Rgs,
Hubert, Poland
 

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Can you post of picture of the device you believe is making the noise? I am not sure what you mean by "flowmeter"... probably a language thing. Maybe the MAF (mass airflow sensor)?
 

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Discussion Starter · #3 ·
Can you post of picture of the device you believe is making the noise? I am not sure what you mean by "flowmeter"... probably a language thing. Maybe the MAF (mass airflow sensor)?
Planethill - indeed - I meant MAF. It is not a noise from MAF exactly but it is close to it and quite loud.
 

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Could be a vacuum hose. There are a couple in that general area. Check them all for cracks or disconnection.

You should also scan for error codes with a Mercedes capable scanner. That will give you a direction to go next.
 

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Discussion Starter · #5 ·
Could be a vacuum hose. There are a couple in that general area. Check them all for cracks or disconnection.

You should also scan for error codes with a Mercedes capable scanner. That will give you a direction to go next.
Thank you for the quick response - I will check all of the connections then. Looking for scheme I suppose that there are two main hoses there?
I have checked the errors by AutelMaxiAp200 for M.Benz, I will try to confirm them by something more professional.
Many thanks Planethill, I will let know when I make some progress with this issue(y):)
 

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Thank you for the quick response - I will check all of the connections then. Looking for scheme I suppose that there are two main hoses there?
I have checked the errors by AutelMaxiAp200 for M.Benz, I will try to confirm them by something more professional.
Many thanks Planethill, I will let know when I make some progress with this issue(y):)
Hmmm. Have you been having any performance or gas mileage issues? If a vacuum leak is large enough to create a "roar", I would think you would feel it when driving. Sluggish, etc. Did your scanner give any leak codes at all? A vacuum leak would definitely throw a code. There are several leak codes (Large leak / Small leak / Really Small Leak :p/ etc). Does the roar happen all the time? Sure it isn't just the air/smog pump? It will roar when on.

Anyway, those codes you reference earlier (p0171 & p0174) usually mean either a vacuum leak or a bad MAF. The baffling part is the "roar" sound. They could be unrelated.

To start, I would remove the MAF and give it a good cleaning with MAF cleaner. Do NOT use anything else, only cleaner designated specially for the MAF. Clear the codes and see if they return. Ruling out a vacuum leak, if the codes return you are looking at a new MAF (in my opinion).

2644738
 
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Discussion Starter · #7 · (Edited)
Hmmm. Have you been having any performance or gas mileage issues? If a vacuum leak is large enough to create a "roar", I would think you would feel it when driving. Sluggish, etc. Did your scanner give any leak codes at all? A vacuum leak would definitely throw a code. There are several leak codes (Large leak / Small leak / Really Small Leak :p/ etc). Does the roar happen all the time? Sure it isn't just the air/smog pump? It will roar when on.

Anyway, those codes you reference earlier (p0171 & p0174) usually mean either a vacuum leak or a bad MAF. The baffling part is the "roar" sound. They could be unrelated.

To start, I would remove the MAF and give it a good cleaning with MAF cleaner. Do NOT use anything else, only cleaner designated specially for the MAF. Clear the codes and see if they return. Ruling out a vacuum leak, if the codes return you are looking at a new MAF (in my opinion).

View attachment 2644738
Genrally, it happend suddenly, with all of these symptoms - 'vacuum air' sound and check with the abovementioned error codes in parallel. Engine has a normal power and acceleration but it shakes at the lower speed, especially when reversing and when standing on 'P' mode increases rpm to 2000 without touching the acceleration pedal.
 

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Discussion Starter · #8 · (Edited)
Genrally, it happend suddenly, with all of these symptoms - 'vacuum air' sound and check with the abovementioned error codes in parallel. Engine has a normal power and acceleration but it shakes at the lower speed, especially when reversing and when standing on 'P' mode increases rpm to 2000 without touching the acceleration pedal.
[Update]
I have checked all of the hoses connected with MAF - they are all in a good condition and there are connected properely.
View attachment 2644952

Only "leak" which I found could be seen on the photo below (I have repaired it by the tape)
View attachment 2644953

I have also disconnected the MAF and cleaned it properely - but, unfortunately, It has not helped.

Codes are still the same and appears all the time - p0171 & p0174.
Rpm at the parking mode are unstable (sometimes suspended on the higher value) and I can hear some kind of quiet knocking from the engine which shakes a little (movies below). But, at the same time, at the highest rpm car rides and accelerates properly.
Rpm1
Rpm2


So now, I wonder if I should change the MAF ? Or maybe there is a simple way to check the leaks without proffesional smoke machine?

Or it could be also connected with the spark plugs which should be changed also?
I am out of ideas :geek::(
 

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So now, I wonder if I should change the MAF ? Or maybe there is a simple way to check the leaks without proffesional smoke machine?

Or it could be also connected with the spark plugs which should be changed also?
I am out of ideas :geek::(
Vacuum leak needs to be tested with smoke. You may have intake manifold flap stuck in wrong position as well. Car needs to be scanned with MB dedicated scanner.
 

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Discussion Starter · #10 · (Edited)
Vacuum leak needs to be tested with smoke. You may have intake manifold flap stuck in wrong position as well. Car needs to be scanned with MB dedicated scanner.
Ok, I will try to test the leaks as well as changing MAF - I will have one to replace on Wednesday. Hope this is small and simple issue at all.

ps should I adapt the new MAF - for example by disconnecting the battery?
 

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ps should I adapt the new MAF - for example by disconnecting the battery?
Nope, it is a sensor not a module...so it is plug-n-play.

@Witek_M brings up a good point. The M272 engine is notorious for broken swirl flap linkage. It does not throw a check engine light though, so it can be kind of stealthy.
 
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Discussion Starter · #12 ·
Guys,thank you for all of the clues and possible sollutions.
Finally - hose 'part-load breathing' A2720181382 (near the MAF) had been cracked because of contact with the metal part of the lpg injector. It was hard to see, but finally I got it. Now everything is perfect and I have the new MAF also :LOL::LOL: Auto part Fuel line
 

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There you go, that鈥檚 full on 鈥渂usted鈥! 馃槅. Glad you figured it out.
 
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