Gas Pedal Problem: Strange Error & Fixes

Hello,

For a long time now, I've been dealing with an issue that, subjectively, doesn't seem to affect performance, but it is concerning.

When you accelerate, a growling or rumbling sound comes from the engine compartment, as if someone is constantly turning on a vibrator . It's a very consistent tone.

However, this doesn't seem to affect the acceleration.

To avoid the engine noise, I now always drive very carefully, using a maximum of half the gas pedal. It easily reaches speeds of 100-120 km/h without any noticeable noise, but above 80 km/h, the road noise almost completely drowns it out anyway.

Over time, strange effects started to appear: After being turned off, it would make a rumbling noise for about a second. Recently, it has also been making a short rumbling sound shortly after starting up, or occasionally when playing with the accelerator and downshifting.

Now, here's the latest observation: When I briefly tap the accelerator while idling, the engine revs up quickly, but only drops back down with a delay. So before: tap -> rumble, today: tap -> bruuuuummmmm.

I think this observation is important for the diagnosis.

Could it be that some component of the ESP system is vibrating? Apparently, the humming sound occurs when a large injection volume is required.

Thank you in advance for your ideas and tips.

AGR (Exhaust Gas Recirculation) and intake manifold valve have been defective for a year.

PS: No, I haven't found anything useful in your (otherwise highly recommended) archive or technical articles. If you like, I can identify the engine codes for you. By the way, is there a breakdown of what those codes mean? For example, what does A-A-Z signify?

Hello,

Why don't you just check to see if anything is loose?
"I'm not aware of anything typical like that, and it's difficult to describe sounds accurately through a forum..."
Only the "VW gods" know why the AAZ engine is called AAZ. It's probably just an ascending "version number" using letters.

Best regards, Rainer.

The intake manifold is making some strange noises. What do you hear when you just turn on the ignition and stand in front of the engine with the hood open?
Can you also hear a humming sound coming from the throttle valve?

Thank you for the previous answers.

I once asked my girlfriend to really step on the gas while I was listening in the engine compartment. Unfortunately, it didn't make that roaring sound because the load apparently wasn't high enough.

The throttle valve can no longer vibrate because the vacuum hose accidentally came loose from it. This hose then accidentally became blocked and has now become firmly lodged in the engine compartment.

Can the solenoid valve on the flap vibrate? Or can the solenoid valve from the EGR system vibrate?

Is there an error message if I disconnect the cables from the two solenoid valves?

Regarding the sound: Do you remember those old teddy bears from your grandmother's time that would make a rumbling noise when tilted? It sounds like that rumble, but it's perfectly even.

The dilemma is that I can't reproduce the humming sound when the engine is running, except when I turn it off. But even then, it only lasts for about a second.

Here's a thought: When the engine is stopped, the motor speed drops to idle speed, and at that point, something like the fuel injection control system wants to inject more fuel to increase the speed again (a feedback loop). That's why there's a brief buzzing sound when stopping, just like under heavy load. Just a thought I had.

Okay, here's a translation of the text from German to English, preserving all '' exactly:

Now, let me ask a question for clarification: Where is the regulation and control of the injection volume and the injection adjustment precisely described in my ESP system? If someone has that link or could briefly explain it to me, that would be great }.

So, the amount of fuel injected is determined by a magnetic field in the upper part of the pump, and the start of injection is controlled at the very bottom of the pump by the injection timing adjuster.
Both, I would say, produce no humming sounds, whether they are working or defective.

Hmm, interesting. So, the injection volume is adjusted via a kind of solenoid? That means the current flowing through the coil in the ESP controls the injection volume?

Could it be possible that the control unit is malfunctioning and rapidly switching the current to the coils on and off? In other words, could the coil be receiving a pulsating current?

That would be at least one explanation for humming that depends on the injection volume .

'If only I knew where the easiest place is to tap into the coil voltage. Then I could check the voltage with my oscilloscope.' (I have one that runs on 12V.)

Sure, just the translation:

"Just like that."

1.7 SDI should be an AKU (Austauschkontrollüberprüfung).

I once read that the TDI engines in the Arosa and Lupo are a short-stroke version of the 1.9 TDI engine.

Hmm??

In the Polo 6N2, the 1.7 SDI engine is the AKU.
The AKU system is also available in the Lupo and Arosa models.

The 1.9 SDI engine should be the AEY type – it has the standard 1.9 DI engine dimensions of 79.5 x 95.5.

Here's confirmation for the "short-stroke theory."
http://www.i-e-l.de/arosa/technik.html

Here, you can also see that the 1.4 TDI is essentially a 1.9 TDI with one cylinder missing .

Okay, please provide the German text you would like me to translate into English. I will only provide the translation.

Hmm, interesting. So, the injection volume is adjusted via a kind of hub magnet? That means that the current flowing through the coil in the ESP adjusts the injection volume?

Could it be possible that the control unit is malfunctioning and rapidly switching the current to the coils on and off? In other words, could the coil be receiving a pulsating current?



Yes, the turnout mechanism (which, by the way, is a torque magnet) is controlled using PWM. However, I don't know the operating frequency.
However, if that humming sound is actually coming from there, you would likely experience significant problems while driving.

Normally, to stop the process, the control panel is set to 'zero flow' and the shut-off valve is opened. There shouldn't be any humming coming from there either...

Try to pinpoint the source of the noise; you mentioned it occurs when you turn it off.

How about 'alternative fuels'? Biodiesel?
Are all the filters working correctly? Etc.

CU Gremlin.

Hi, is there an air conditioner installed, and is it as hot where you are (outside temperature) that the unit is running?

Best regards, Rainer.

Yes, the turnout mechanism (which, by the way, is a torque motor) is controlled using PWM. However, I don't know the operating frequency.
However, if that humming sound is actually coming from there, you would likely experience significant problems while driving.


CU Gremlin

Hi there,
I drive a G4 ALH. The car has a hands-free phone system installed. It seems to have a ground fault or a ground loop. Anyway, when the engine is running, you can apparently hear the sound of the fuel injection pump operating while talking on the phone.

I believe it's related to the ESP because the disturbances disappear when I release the accelerator pedal (pure thrust mode), they are most pronounced in partial load operation (duty cycle), and become significantly less noticeable again at full throttle (approaching 100% duty cycle). When I press the clutch in thrust mode and the ESP injects fuel again, the noise immediately reappears (as it does in idle). I would describe the disturbance as a kind of hissing sound. I suspect it's within the frequency range of 8-10 kHz (white noise).

It could also be related to the control of the VTG (variable turbine geometry) or the EGR (exhaust gas recirculation), but I don't think that's likely.

Therefore, I would rule out the possibility that the humming is caused by the ESP control system.

Could it possibly be caused by a wave in a plain bearing that has too much play and starts to oscillate at a certain speed range (like the old starters that made strange noises when they were disengaged)?

Greetings.

Eike.

First of all, thank you, Gremlin, for the thorough discussion.

@Rainer: No, my car (manufactured in 1998) is quite basic in terms of equipment; it doesn't have air conditioning. As I said, there are no subjective issues during operation. I haven't detected any leaks so far either. If there were a leak on the light concrete outside my house, I would immediately see a stain.

'@Dieselmartin: It's actually an AKU (general inspection), as stated on the cover page of the maintenance booklet.'

'@Gremlin: I've driven 50,000 km on biodiesel, but two months ago I had to replace the fuel filter. Now I'm using regular diesel until it gets warmer. The humming noise didn't start when I switched back to diesel.'

Could it possibly be caused by a wave in a plain bearing that has too much play and starts to oscillate at a certain speed range (like the old starters that made strange noises when disengaging)?

Hmmm, the humming sound doesn't occur starting from a specific enginespeed, but rather from a certain engineload, meaning from a specific torque level. Are there any plain bearings in the ESP that are increasingly less radially loaded with increasing oil flow and could then start to spin? That would be an attempt at explanation in this context.

It's getting really mysterious slowly , but thankfully everyone is working diligently on the puzzle .

The vehicle has a hands-free system for the phone. It probably has a ground fault or a ground loop. Never mind, anyway, when the engine is running, you can apparently hear the control signals of the fuel injection pump when you are on the phone.


The sound is definitely not coming from any of the speakers, so that rules them out.

General question: Can I disconnect the cables from the solenoid valves (AGR and throttle valve)? Maybe one of the solenoid valves is making a buzzing noise. Perhaps I should build an adapter for VAG-Com. Besides, I'm planning to install a notebook for playing MP3s in the car anyway. It has COM and USB ports available.

Sure, here is the translation of the text from German to English:

'cu' is a Spanish abbreviation for 'con usted,' which means 'with you.' It is often used in online communication and texting as a way to express affection or intimacy.

Here are some examples of how 'cu' can be used:

* 'Te amo, cu.' (I love you, with you.)
* 'Eres mi todo, cu.' (You are my everything, with you.)
* 'No puedo vivir sin ti, cu.' (I can't live without you, with you.)

It is important to note that the use of 'cu' may be considered informal or even inappropriate in some contexts. It is best to use it only when communicating with people who are close to you and who understand your intentions.

SeatArosa1.7SDI wrote:

General question: Can I disconnect the cables from the solenoid valves (AGR and throttle valve)? Maybe the solenoid valve is making a buzzing noise?

Hi,

Disconnecting the cable is possible. It will leave an error entry, which, as far as I know, is deleted after 50 engine starts without any errors (i.e., when the connector is reconnected).
Otherwise, nothing is likely to happen.

Even if the warning light comes on or the car goes into limp mode, it will be "forgotten" again after a maximum of 3 engine starts (with the connector plugged in).

Yes, please go ahead and disconnect the cables.
Nothing happens except that the engine might not start.
Then you just plug everything back in again.

Yay, I got it! The solenoid valve for the EGR vacuum control is humming! - And specifically, whenever the EGR valve is supposed to close (control air = OFF), it hums or sucks in through the venting hole of this 3/2-way valve.

It wants to buzz, so be it. I don't care .

Then it simply won't receive any more vacuum air . I should have done that right away.

Despite the issue, this defect provided a learning experience: it gave me a precise sense of the AGR valve's operating point through acoustic feedback. The conclusion is: the AGR valve (when not 'defective') is surprisingly often active throughout a car's lifespan. This explains why the intake manifolds are so often completely clogged with soot and grime.