G4 Performance Issues: AGR Problems Persist.

Hello everyone!

This weekend, I took a look at my girlfriend's TDI G4... I checked all sorts of things according to the technical articles, and even tried to bypass the mass airflow sensor (MAF) with a diode.

So, the thing with the diode didn't really achieve anything (VAG-COM consistently showed 500 mbar), and it even worked better with the MAF sensor...

"Then I also removed the hose connecting the lambda sensor to the EGR valve... and there's a noticeable oil film inside that rubber hose. It looks like it's coming from the EGR valve side. Is that normal?"

I now suspect that the AGR (Abgasrückführung system) is not closing properly or is playing some other funny tricks on us.

"Definitely, there's a loss of power, increased fuel consumption, and quite a bit of soot at higher engine speeds... during the last annual inspection, we almost failed the emissions test... I'd say that's a pretty strong indication that it could be the EGR valve."

To top it all off, the diagnostic connector has failed again. It seems to be having problems with the laptop's power supply, and now I can't even log any more data.

"Fortunately, it wasn't a major issue... so, at idle, I had approximately 380 mbar of air mass flow. When I pressed the accelerator, it increased to around 500. I couldn't perform a full-load test at 4000 rpm because the connector melted right there. However, when reviewing previous test runs, I never saw the value exceed 500, which is what it should be for an MKB engine with AGR, according to the test results shared in this forum."

Boost pressure and other values, according to the "procedure for troubleshooting performance loss in threads," are all normal.

I was actually just wondering if there's another way to test the AGR (Abgasrückführung).
Ultimately, I'll probably just end up removing the AGR (Abgasrückführung - exhaust gas recirculation system), and then we'll see what happens!

I would be grateful for a few tips!

Okay... so much buildup like in the pictures in the technical article must have already accumulated, even in the cylinder head. It's probably going to be a pain to clean, especially towards the cylinder head... I guess it's probably impossible to do without removing it?

Thanks in any case for the suggestions...

Hello,

"First, make sure the diagnosis is correct, then perform a basic adjustment in the main control unit (ECU) 3 and observe the mass airflow values with the EGR valve fully open and fully closed. This will give you a preliminary indication of the condition of the EGR valve."

Then, run a full-load log with a 3-8-11 setting, and also try it with MWB 4 (start of injection).

Air mass is measured in mg/stroke (milligrams per stroke), not mbar. The air mass at idle should be around 370 mg/stroke without EGR (Exhaust Gas Recirculation), and approximately 210 mg/stroke with EGR fully open.

The whistling sound can also be caused by a leak in the charge air cooler system.

The oil in the intercooler hose comes from the crankcase ventilation system and possibly from the turbocharger, and this is normal to a certain extent.

Malte1408 wrote:

Hello, Bring the diagnosis into order and first perform a basic adjustment in the main control unit (ECU) 3, and observe the air mass values with the EGR fully open and fully closed.

Then you can get a preliminary idea of the condition of the EGR valve.

Hi, thanks for the info. How do I perform a basic adjustment like that? And more importantly, how can I tell if the AGR (Aktivkohlefilter) is on or off?

While idling, I've already seen the 350mg/h value that I described earlier!

However, when accelerating or under full load, which is when the EGR valve should be closed and the full air mass should be applied (approximately 800 mg/stroke), I didn't see any of that!

At partial load, the value is usually around 500 mg/H.

Sure, here's the translation:

"lg" is a German abbreviation that stands for "liebe Grüße," which means "best regards" or "warm greetings." It's commonly used in emails, letters, and other forms of communication to express affection or goodwill.

Hi everyone,

I finally have the car in my garage... it wasn't easy, considering we live in different states.

In the meantime, we were also on vacation -> in the Großglockner area... we also drove up the High Alpine Road... Well, what can I say... just before the toll booth, she suddenly said: "... now it's doing that jerky thing again... and it's not working anymore..."

*gg* We then drove the second car with the accelerator fully pressed... We didn't go any faster than 50, and the tachometer was stuck at 3000 RPM.

That's all there is to say about the performance loss...

Now, let's get to the "more tragic" part of the story...

"I removed the AGR (Abgasrückführung) valve today... unfortunately, the condition inside the AGR valve isn't great. There's a 2-3 mm thick layer of oil and carbon buildup... well, of course, that also gets drawn into the intake manifold."

I guess I'll have to take it apart and clean it thoroughly now.

What's the situation after the air intake manifold? How many more air ducts leading into the engine are there? They should actually be cleaned too, right? Does that mean taking the cylinder head off?

What happens if such pieces of soot break off and fall in, or if, while driving, someone is unaware of it and they get sucked into the engine? Surely that's not good either, right?

I'm curious to know who has already done the dirty work of cleaning this up.

If anyone has any tips, please let me know!

Sure, here's the translation:

"lg" is a German abbreviation that stands for "liebe Grüße," which means "best regards" or "warm greetings." It's commonly used in emails, letters, and other forms of communication to express affection or goodwill.

Hello,

Okay, I replaced the AGR valve some time ago... and I removed and cleaned the intake manifold.

There was quite a bit of dirt inside.

The car then performed a bit better; the power delivery and other aspects seemed to be working correctly again.

According to my friend, it's not quite as good as when it was new, but it's still good.

Okay, so yesterday we went on vacation, and during the drive, we had that problem of sudden power loss twice again.

Okay, so it wouldn't go any faster than 110 km/h, and the engine revs just wouldn't increase... I pressed the accelerator all the way, but nothing happened.

After the engine is turned off, the problems disappear.

Does anyone have any more tips?

Sure, here's the translation:

"lg" is a German abbreviation that stands for "liebe Grüße," which means "best regards" or "warm greetings." It's commonly used in emails, letters, and other forms of communication to express affection or goodwill.

"The sudden loss of power is the emergency mode! Turn the ignition off and on again, and it should return to normal. Read the error codes! It's normal for a slightly oily, sooty residue to form, up to 2mm thick."
First, read the error memory before you start removing parts unnecessarily!

The AGR (Abgasrückführung - exhaust gas recirculation) that I exchanged definitely had a defect.

The problem is that I haven't found any error codes in the diagnostic memory so far. That's why I've been thinking about the limp-home mode, but I've always assumed that if there's a fault, it should also be logged.


"By the way, the EGR valve was stuck... and the oily residue you're talking about was actually carbon deposits, about 4mm thick, that had broken off inside the intake manifold."

Hi,
Have you thoroughly examined the charge air cooler system (hoses, hairline cracks in the intercooler, etc.)?

Does the loss of power affect the driving experience? (Only when accelerating fully...)

Hi, the charging cable seems to be in order... at least, I haven't been able to detect any loss of pressure anywhere... visually, and by listening and feeling.

As mentioned, the power loss is very sporadic and, above all, doesn't always happen... it's like a failsafe mode, but without any error messages.

"However, the power loss likely occurs under load... The first time it happened was when accelerating on the highway... The second time it was when driving uphill towards a mountain pass."


Sure, here's the translation:

"lg" is a German abbreviation that stands for "liebe Grüße," which means "best regards" or "warm greetings." It's commonly used in emails, letters, and other forms of communication to express affection or goodwill.

Hello, I'm reviving an old thread...

Quite some time has passed.

But the car is still giving me trouble...

"In the meantime, the AGR (exhaust gas recirculation valve) has been replaced, and the entire intake manifold has been cleaned of soot deposits, which were, in some areas, almost 1 cm thick."

So far, so good.

However, even after the repair, the car still occasionally experiences "extreme" power loss.
Basically, I think he should be doing better... but sometimes it's just like a switch gets flipped and then nothing works anymore.


The following memory error frequently occurs:

17958 - Charge Pressure: Control Deviation.
35-10 - - - Intermittent


We've also taken it to a VW workshop before, but they couldn't do anything about it.

Incidentally, one of the vacuum components was created (I don't remember the exact name right now, but it's the one that controls the EGR valve).

Does anyone have any other suggestions on how I can make my girlfriend happy again?