Audi A4 2.0 TDI: Jerking/Hesitation Under Load

Hi,

Maybe someone will take a look at my log and give me a tip on a PD unit or something?
He only does it intermittently, and even at idle, it sometimes seems to stumble a bit.

Hi,

It's funny, I was working on that exact engine yesterday. The customer had a similar problem; occasionally, you could feel a "misfire" on one cylinder while idling.
Otherwise, there was nothing else to note; the engine ran smoothly while driving. Despite a brief troubleshooting attempt, I didn't really become any wiser.
The next step would have been to check for air in the fuel system, but the engine was already producing full power.
The error memory was, of course, empty, and the idle speed control showed excellent values. As soon as the engine speed was slightly increased, to about 1200 rpm, it ran perfectly.
The load on the motor didn't really have much influence; all the sensors showed plausible, stable values.
The car is running well, with 135/136 kW (~185 hp) in the subsequent measurements .

Best regards, Rainer.

Well, this one definitely doesn't!
He probably runs, but the problem is severe - above 3000 RPM, it sometimes has really bad misfires! At 200 km/h on the highway, it can really shake and cause headbanging.

I've gathered a few more data points - I think everyone will agree about the readings!

But take a look for yourselves - I can also post the Excel files if you like - but I think this is enough .

During another trip, I also occasionally saw status 128 on all four .
Does anyone know when it will be fixed? 'GDP calculation not possible.'
But even there, always pre-heat cylinder 2 to 16 several times!

Hi,

Loose wiring or a faulty control unit? It's unlikely that three PD elements would fail simultaneously, right?
Normally, the injection pressure (BIP) is equal to the closing of the solenoid valve, meaning you can determine when it's "closed" by observing the current flow in the coil. I don't know how it's done with piezo injectors, but theoretically, it should also be possible to determine the BIP by analyzing the current flow: the BIP would be when the current flow is 0 and the voltage at the injector is 100%.

Best regards, Rainer.

Let's start by replacing the valve for cylinder 2, and then we can investigate further. It might also just be a software error from the control unit or something like that.
During one trip, I experienced this issue a few times with status code 128. In another instance (see the log above), it didn't occur at all; instead, all cylinders reported values from 0, except for cylinder 2, which reported status code 16 when it was under load and experiencing vibrations.

When idling, it occasionally has those jerks (as you mentioned), and cylinder 2 is the furthest out in the negative direction, while cylinder 4 is the furthest out in the positive direction, each by either or -1, which should actually be compensated for by the electronics.

It's still strange . I actually expected him to sometimes shift gears more aggressively, but he mostly just jerks forward, especially in 5th gear on the right lane. Then you have to pull out and accelerate - sometimes it works, sometimes you think the car behind you is about to crash into you because it just sputters for 2-3 seconds without actually accelerating.

Okay, I replaced the PD element (likely referring to a glow plug or similar component) in cylinder 2, and the misfire is gone.
But something else that I've noticed recently:

MWB 4, field 2 (start of funding), is generally idling at 1.9 n.OT.
The setting range is from 4 bar vacuum to 2 bar pressure.
Since the engine still has occasional slight 'jerks' at idle, I think it might be related to that.

'The question is, how do you get someone who has a different opinion?'
I haven't found anything specific related to that (the synchronization angle is within the normal range of 0.5-1).

EDIT-P.S.:
Can I have the instructions https://community.dieselschrauber.org/en/viewtopic.php?t=5408?
'You can also use this with that engine, as it has two adjustable camshaft gears.'

Hi,

How can one out of four defective PD (Power Distribution) units bring the performance down to zero?
"I'm a bit surprised; it's possible that the control unit just glitched. Unfortunately, I don't have any other suggestions for the rest of the issue."

Best regards, Rainer.

Okay, the performance was there, but it had some serious interruptions due to the failure of the second cylinder element. How the MSG (presumably a control module) reacted to this is another matter. The interruptions with status code 16 have disappeared with the new unit, and the car now easily reaches speeds above 210 km/h without any interruptions. At least, that's the case so far. I also checked the cable, but both the contacts and the cable showed no abnormalities.

Now, the only remaining issue is the matter of the LL (likely referring to a specific legal or regulatory aspect) and the unusual value of the start date for the funding.

Let's adjust it a bit on Monday so that it ends up around 1 bar of vacuum (which should be right in the middle of the regulation range), and then we'll see what the idle speed is like.

I can't explain why he would choose to run so close to the border.
An A3 BKD today was priced between 0.4 and 0.6 times its original value. But can these engines, despite some modifications but the same target values, be considered comparable?

I understand that the BMM (8V with particulate filter) cannot be directly equated with the other engine, but I believe that, because the BLB has a balance shaft unlike the BKD, it could potentially run similarly.