Engine Misfire: Causes and Solutions

Hi.
"On my A4, model year 2000, with the AJM engine, I'm experiencing a shaking at idle. It feels like sitting on a vibrating plate. As soon as the RPMs increase, it disappears. It's also not noticeable while driving. We noticed this on the way home from picking up the A4 from the dealership, and we immediately took it back. The dealer said the flywheel was broken. The problem was gone after a few attempts. The car now has 120,000 km on the odometer. This shaking has occurred occasionally before, but it was only a mild vibration and disappeared quickly. Now it's constant and quite severe. Could it really be the flywheel? Shouldn't it also be noticeable at higher RPMs?"
Best regards, Bolzer.

hello

It would be best to check the measurement blocks for the idle fuel quantity of the pump-injector elements using VCDS.
I'm not sure if the MSG can still be properly calibrated if the PD elements are too far apart.
It can lead to a rough idle. We experienced the same issue with a colleague's car.
At a mileage of 80,000 km, the elements 2 and 3 were worn out.

Best regards.

hb2000

hb2000 wrote:

if the `pd` elements are too far apart. It can lead to a rough idle. A colleague of mine experienced the same issue at a mileage of 80,000 km, and in his case, elements 2 and 3 were worn out.

Hi,

80,000 km is AFAIK a ridiculously low mileage for a PDE .

Could it be that the PDUs were still from the initial production runs and already had high tolerances from the factory?

Or have you noticed any defects in the PDE that can only be caused by wear and tear?

hi ulf

I can rule out wear and tear given the extremely low mileage.

At a mileage of 55,000 km, all the particulate diesel engine (PDE) components were still within the tolerance range.

Biodiesel has never been used in this car since I started taking care of it.

Based on their age, they might still be PDE (presumably a company or product) from the first generation.

Best regards.

hb2000

hb2000 wrote:

Wear and tear can be ruled out given this ridiculously low mileage. At a mileage of 55,000 km, all the particulate diesel engine (PDE) components were still within the tolerance range.

Well, if the PDE falls outside the tolerance range within approximately 30,000 kilometers - how else can you explain it other than with some form of wear?
While not necessarily exhibiting the symptoms commonly associated with nozzle wear – such as altered hole geometries leading to unusual spray patterns, etc.

Hi.
I took a look at MWB 1 and 18.

Injection quantity: 6 to 6.3 (target: 3.0 to 11.0)
Target support duration: 5.6 to 6.1 (Target: 5 to
Status valve for PDE 0.0 (target 0).

Therefore, the PDE would be I.O. (In Order).

Let's go back to the flywheel. Is it possible to check the flywheel while it's installed?
Best regards, Bolzer.

hello

I think it's probably in MWB 13 where you can see the PDEs listed together.

The idle speed control of the PDE should operate within the range of '-3.00' to '+3.00'.

'What's interesting are the largest deviations in the PDE values among themselves.'

The greater the deviation, the more worn the PDE is.

Best regards.

hb2000

Hi.
I checked again today what it displays under MWB 13.
The values are -0.68, -0.29, 0.28, and 0.68.

Best regards, Bolzer.

The values are generally okay! According to VW/Audi specifications, negative values should not be considered. Positive values should not deviate by more than 1.00.

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

"Micha"

Hello.

The values are quite acceptable.

According to VW/Audi specifications, negative values should not be considered.

Negative values are just as important to consider as positive values. The key is to pay attention to the deviations between them.
These values should be relatively close to the 'ideal value of 0,' both positive and negative.

You can most likely rule out PDEs as a source of error.
It seems the problem is coming from a different component, which needs to be investigated.

The values are -.68, -0.29, 0.28, 0.68.

Are you sure you mean -0.68 with the first value?

Regards,

hb2000

Hello, I had a faulty dual-mass flywheel (DMF). The symptoms were severe shaking at idle when the engine was below 70 degrees Celsius and a rough running engine. When you start the car, try turning the air conditioning on and off. Does the shaking increase or decrease? Does the engine sound rough when accelerating? Have someone else drive the car while you sit in the passenger seat. Does it make a loud humming noise between 2000-3000 RPM at a constant engine speed?

CU moby.

'I spent 3 years searching for the same error on my car. I paid over €600 to specialized workshops for troubleshooting, and the culprit turned out to be a €75 serpentine belt idler pulley on the alternator.'

Check if your serpentine belt is wobbling!

Regards,

Manuel.