Leichtes Ruckeln zwischen 3000 und 4000 U/min Hilfe!!! | Posts 16+

I didn't want to offend anyone or anything like that, I just felt a bit attacked in my abilities, but it doesn't matter now, we're not in kindergarten or .

*Rain offer of peace*

Back to the topic:

The intercooler piping is fine; the hoses were replaced only 2 months ago. The boost pressure is also okay; a test drive was conducted, and I was informed that all the measured values were within the normal range. I had to rely on that statement because I didn't have a laptop or the necessary software/hardware myself.

As I said, you don't notice anything until 3000 RPM; the car has been chipped and it runs really well up to that point. Even after the quarter hour, when the shaking stops, it runs like a dream, without any issues.

We initially thought it might be the NBF (Negative Battery Fuse) that was causing the issue, and that the LMM (Lambda Measuring Module) data was being stored in the control unit as a result. 'So, as I said yesterday, the part was replaced. And this morning, the jerking started again, and the Mass Air Flow sensor (MAF) was again stored as an error in the system's memory, which was read out today.'

And the ironic thing is, the engine doesn't misfire when the mass airflow sensor (MAF) is faulty! So, I'm ruling out the loose connection/power supply as the cause.

It's just a bit suspicious, first the accident repair, then the car was picked up, and then no more progress --> the mass airflow sensor (MAF) was broken, the MAF was replaced ---> but now there's a jerking issue .

Please bear with me, I just want my device to work properly again [/b].

Okay, so let's actually start properly troubleshooting this...

What's concerning me is the recurring LMM error with a short circuit to the positive terminal.

Okay, I'm going to start troubleshooting by checking the wiring harness.

Okay, so first check the connector on the MAF sensor, then the connector on the EDC itself. If the pins and contacts look normal, use a decent multimeter and connect it to the beginning and end of each wire. Then, start moving and pulling the cable bundle in all directions. Breaks within the wires are rare, but if they occur, they are usually severe. I suspect there's a contact problem in one of the connectors.
It's possible that your NBF error is related to this as well.
We had water in the engine control unit connector before, and the control unit was located inside the passenger compartment (in the footwell). However, it was completely dry, with no traces of water, no signs of ingress, nothing. We more or less found it by chance because we wanted to test the control unit as the last component. A waterfall... anything is possible.


CU Gremlin.

(*) I'm looking for a multimeter that is FAST, so I can see changes in resistance. Nothing cheap or low-quality!

Hi,
What kind of accident was that? Could one infer the existence of damaged parts from this?

On a different note: These intermittent errors sometimes originate from relay 109, which is related to the power supply. Speed-dependent vibrations may also have an influence in this case.

Or, alternatively, the entire electrical system might be faulty because, for example, a grounding strap has a poor connection, or the alternator regulator or its brushes are worn out.
I experienced a slight vibration around 2000 RPM. My friend's gasoline car actually started misfiring this winter, especially when the radio was on; it ran reasonably well without it.

Ultimately, there must be a reason why the mass airflow sensor, which never causes problems, is now failing for the fourth time, assuming it is actually the problem.

I wouldn't completely rule out the possibility of loose or corroded contacts.

What happens if the boost pressure gets too high? Shouldn't the engine control unit (ECU) reduce the fuel injection amount, etc.? If everything is back within the normal range, then proceed. I've experienced this with my 1Z engine before. Sometimes, there wasn't anything stored in the error memory. And the mass airflow sensor (MAF) error either appears randomly or as a consequence of the problem.

I would recommend getting a VAG-COM diagnostic tool and an adapter. Then, take some logs in the area you suspect is causing the problem, and things will become clearer. Otherwise, you'll just be guessing and throwing parts at it! Put the replaced parts back on and say goodbye to the workshop. Who knows what they told you about turbo boost, etc...

MTM A6 2,5 TDI wrote:

THE WIRING AND POWER SUPPLY HAVE BEEN CHECKED!!!

Forget it!
Almost no workshop can do anything with the "short circuit after pulse" error.
Just to be clear: Your LMM (likely referring to a Lambda Sensor or Mass Air Flow Meter) is not defective, and it can be replaced many times.
"Kurzschuss mach Plus" simply means that the mass is no longer present (missing... and sometimes intermittently). So, it's most likely just a cable issue.
Finding a mass error is either a matter of luck or a pain in the ass. Work.

4 defective mass airflow sensors, never in a million years.

@MTM, what have YOU personally checked or done to troubleshoot the issue?

Okay, here's what I did myself:

-Control unit removed, contacts checked on both the control unit and the connector (all okay).
- Removed the tuning chip and installed the original chip (the problem still exists even with the original chip).
- Reinstalled the old LMM (defective one) and drove with the stock chip (THE JERKING WAS GONE!!!)
-Put the tuning chip back in and drove with the old mass airflow sensor (THE JERKING WAS GONE!!!)
-Reinstalled the new LMM (BUT THE JERKING WAS BACK!!!)
- Checked the contacts on the connector to the mass airflow sensor (MAF sensor) (No oxidation was present, but I sprayed them with contact cleaner anyway - it didn't help).
-Have a friend with access to a Bosch service center test the MAF sensor connector (everything was okay, but it was tested very early on, which then revealed that the MAF sensor was defective).
- Replaced all overflow/return lines on the injectors (they were already old and porous).
- Replaced the gasoline hose leading to the diesel pump (it had a significant indentation from the engine cover and was also damp).
-The intercooler system was replaced 2 months ago (2 pressure hoses were changed).

Audi did the following:

-3x LMM replaced.
- Checked wiring and power supply (according to...). Okay, everything's fine.
- Needle position sensor replaced (did not improve the problem at all).
- Test drive completed (according to...). 'All Audi sensor data blocks are okay, including boost pressure, etc.'
-Tomorrow/Today, I'll have to change the LMM again (I don't really believe it will make a difference).


I'm just surprised that the jerking doesn't occur with the faulty mass airflow sensor (MAF). It makes sense that if the MAF is broken, it can't regulate anything and therefore can't cause any jerking. On the other hand, Audi's technical support and a friend of mine say that the cables are fine, and there is no relay because the mass airflow sensor (MAF) is directly connected to the engine control unit (ECU).

It seems like only the control unit (STG) itself remains. However, if there's a fault within the STG, my knowledge isn't sufficient to locate it on the circuit board or elsewhere. I'm not sure if the STG could be damaged by being left untouched for 5 weeks. As I said, the jerking started only after we installed the new blade alignment gauges.

Regarding the accident repair, it was just a rear-end collision at approximately 25 km/h.
The car was normally repaired (bodywork) and a new tow hitch was installed. The parts that were replaced are listed at the very top of the thread.

MTM A6 2,5 TDI wrote:

Then it probably only leaves the control unit (STG) itself.

Sure, here's the translation:

"Again:"

"Please check the grounding cable for the mass airflow sensor (MAF). If there isn't a clear grounding potential, it can cause problems with reading the sensor values, which can then fluctuate (even with a constant airflow) ..." This results in a jolt.

It's also possible that there's a slight fluctuation in the reference voltage (I believe it's 5V from the motor control unit). This would cause the measured values to fluctuate as well. This can also be easily achieved by generating and applying an external reference voltage.

Okay, I suspect there might be a broken wire in the cable leading to the mass airflow sensor, or that the individual wires inside the cable aren't properly connected to the contacts in the connector.

Hi everyone,

Yesterday, I went back to Audi again and had them reinstall the old mechanical fuel distributor, as the new one didn't provide any improvement at all.

Then the mechanic who had been working on the car asked me what was actually wrong with it, since he was there almost every day. I explained the whole problem to him again.
He then told me that it could actually be due to three things: the mass airflow sensor (MAF), the diesel pump, or the engine control unit (ECU), although he said that the ECU is the least likely cause.

He said that if the injection timing is not correct, it can also cause that kind of jerking. So, if the injection timing is too late, the engine has no power. And if the injection timing is too early, it starts to smoke (which it does a lot), and there can be jerky movements, as I mentioned before.

Then it occurred to me that I had the timing belt replaced at the end of September last year. I didn't have this done at an Audi service center, and consequently, I'm not entirely sure if the fuel injection timing has been properly adjusted (which is quite a delicate process) or not.

'Then I told them to read the data blocks from the diesel pump. At that point, the nice Audi mechanic said, 'Well, I can't imagine that it would have anything to do with the problem, because either the injection timing is correct or it's not.'' 'That's a great answer,' I thought, and then I said, 'Do it anyway!'

And there you have it: According to the table, for measurement block 'Injection Start' (which was measurement block 3), the value should be AT LEAST 70 and AT MOST 82.

Mine fluctuated between 60 and the highest it ever showed was 63 (measured at idle)!!!

Quote from the Audi master: 'Well, I'd say that's definitely the absolute lower limit of acceptable tolerance.' I was just thinking, 'Argh... you just said either it's true or it's not, so what I saw wasn't true!'


Okay, here's my question again: In my opinion, he's injecting fuel too early, which would explain the increased black smoke. This indicates an incomplete combustion, which could be causing the jerking or stuttering. Furthermore, at higher engine speeds, the injection timing also changes, and there could be an even greater deviation. Could this deviation I described, which was measured at idle, lead to such a problem?

To describe the jerking or abrupt stopping again, I feel that 'jerking' or 'hard stopping' isn't quite the right expression. I just thought of something that captures it perfectly:

It's like someone is accelerating flat out in first or second gear and then lightly touches the brakes.

Furthermore, I'm also looking at the turbocharger boost control valve. I've read that if it has a mechanical defect but still functions electrically, it won't register an error code in the system, and this can lead to the very symptoms you're describing, as if someone is constantly lightly pressing the brake pedal.

It would be helpful if you could tell me more specifically about the measurement block and how it might be relevant.

If I can completely rule out these two things (fuel injection pump/start and boost pressure solenoid valve), then I'll probably need to replace the air flow sensor (MAF) hoses, and if that doesn't work, I'll have to replace the engine control unit (ECU).

Thank you in advance for all your help and efforts so far .

Is the :xshaking now gone or not?

No, it is still there.

ahem...

'I think there's something in the error memory about a short circuit in the mass airflow sensor (MAF) to the positive terminal. Unfortunately, I don't understand how that relates to your starting problem! How about you finally start investigating the issue yourself instead of just complaining?! I can't read these long stories anymore. In my opinion, you should start taking measurements in the relevant speed range and post the values, or continue to rely on your Audi dealership. The way things are now can't continue. You're just gathering information here, getting ripped off by Audi, and then complaining here. So, get some tools and post something factual and official. Pasta...'

@joergs

I was actually just hoping to get an answer regarding the measurement block described above.

Sometimes, the error memory contains so much information, but it's often inaccurate.

Okay, here's the translation:

'With a friend of mine (who drives an S4), the error memory showed 'oxygen sensor defective.' Turns out, the oxygen sensor was fine; it was a pressure sensor that had burst!'

Sometimes, displayed errors can be secondary effects, something you'll know just as well as I do. So why should I tear apart my wiring harness, only to have someone later say, 'Oh, we could have told you that!'?

And why can't it be that, due to a lack of fuel or something similar, the mass airflow sensor (MAF) is providing incorrect readings or malfunctioning at that moment, leading to incorrect fuel regulation and then triggering an error code? Is there still some kind of communication happening between the STG (Steuergerät - control unit), the LMM (Luftmassenmesser - mass airflow sensor), and the pump, or not?

And no one is whining here. If you've read what I've written, you've probably seen that Audi was telling a bunch of lies about what they did and what they didn't do.

It's just that this is my first diesel car, and I have to deal with these kinds of things, so some information is necessary. And, as you've probably read, I haven't been completely idle either.

Do you now understand that 'tools' refers to the diagnostic software and a laptop, which I don't have and won't buy because of a problem I'm having.

Those who no longer feel like it, or who find it bothersome, don't have to respond .

Regarding your wiring harness modification, I think the process shouldn't take longer than 20 minutes. Disconnecting 4 wires from the connector and running them to the control unit with free wiring is guaranteed to take no longer than that. This should definitely help you rule out any issues with the mass airflow sensor (MAF).

Regarding VAG-COM and a laptop: Yes, that's what I mean. If you want to become independent of Audi in the long run, you need that. Just consider the time you spend visiting Audi and calculate that in terms of money. You'll quickly realize that VAG-COM would have been the more cost-effective alternative. And this definitely won't be your last problem...

Regarding the fuel shortage: yes, that can cause jerking. It can also lead to misfires. However, I don't think the error memory will constantly show a short circuit to positive for the mass airflow sensor (MAF).

Okay, now go to Audi and have them adjust the start date for the subsidy, and then we'll see what happens.

Do you now understand that 'tools' refers to the diagnostic software from here and a laptop, which I don't have and won't buy because of a problem.

@MTM A6 2.5 TDI:
It would be enough if you purchased the adapter kit for 69 euros and borrowed a laptop with a COM port from a friend. You don't need to buy your own right away! And I think 69 euros is reasonable, considering how much Audi has already added to the price.

If you don't happen to know anyone who has a laptop (which I find hard to believe), then the cheapest one you can find on eBay for under €150 should suffice.

Regards,
Private.