A4 BPW vibrates/jerks

I installed a used engine in an A4 with a BPW motor. The old engine had compression of 18 bar on cylinders 2 and 4, while the other cylinder had 0 bar. During the leak test, air was escaping from the oil filler neck, so I suspected either a problem with the piston or the cylinder.

I ended up installing a used engine with supposedly 160,000 km on it.

It only vibrates or shakes when accelerating.
In the MWB 23 (likely a diagnostic report), I'm seeing a value of -50 on cylinder 3 during normal driving, while the other cylinders are around -10. When accelerating, cylinder 3 goes up to -90.
In MWB 13, the readings for cylinder 3 were approximately -0.94, while for cylinder 1 they were approximately +0.94.

I've only seen such high negative BIP values on 16V engines when the valve guides in the cylinder head are oval-shaped.

Has anyone experienced this with an 8V engine before, where the copper gasket was leaking even though the engine seems to be running normally? Or could it be that the middle O-ring is defective?

Hello,

Differences in the idle speed control (MWB13) of less than 2 mg/H are generally not critical.

I don't have anything specific in mind for comparison with MWB23 right now. Perhaps you could simply search for corresponding values within this forum and compare them?

Quote:

Has anyone experienced this with an 8V engine before, where the copper disc was leaking even though it seems to be running normally, or is it perhaps a defect in the middle O-ring?

Certainly, it's rather unrealistic at 160,000 km. My advice would be, when rebuilding the engine (installing a used engine), to replace and adjust the injector nozzles. This way, you know the condition of the cylinder head and can usually avoid further issues for a while.

Best regards, Rainer.

"Has anyone experienced a Torque Phase Indicator (TPi) issue with 16V engines when the cones are oval, resulting in the Best Ignition Point (BIP) showing values around -90? I encountered this problem with one engine as well."

It's the same with this one, but I've never experienced that issue with the 8V models.

I'll probably have to remove the component on cylinder number 3 to take a look. I'll also replace it with the one from cylinder number 4 at the same time, so that we might be able to draw some conclusions later.

I need to check with the customer again about the actual mileage of the vehicle, as the customer provided the engine.

The engine control unit (ECU) had been modified with a performance tune; I checked it out and installed the original software.

The support duration parameters were increased by as much as 40%!!!!, and the injection start time was raised by 2.5 kW. I strongly suspect that this is why the old motor failed.

High negative values in the GDP (Gross Domestic Product) indicate a fuel shortage. The numbers displayed in the MWB (Multifunction Display) represent the time it takes for the solenoid valve on the PDE (Pump Deno Düse - pump nozzle injector) to open/close.
If that's the only injector, then either the zero rings are damaged (especially the one in the middle), or the high-pressure pump is faulty. In essence, the diesel fuel is flowing directly back into the return line.
Most often, the pressure values are also higher downstream of the positive displacement pump (i.e., further away from the tandem pump). This is because the leak reduces the upstream pressure.
But you can only take anything displayed there seriously if the correct data dump for the model is currently loaded onto the control unit.
"Why don't you install a new engine control unit (ECU) from the old motor just for testing purposes?"

I know what the positive and negative values mean.
I was wondering if the copper ring could also be leaking.
The 16V engines behave the same way: they exhibit high negative values and jerk when accelerating if the cone is oval.

I'll check back again tomorrow or on Tuesday. Today, I'm going to do another logging run and will post the results here.

Thank you.

If the copper ring is leaking, it forces exhaust gases into the injector bore.
It only affects the fuel supply and pressure when the lower O-ring is also fully engaged.

Right after starting the engine and during the initial acceleration, I experience a noticeable jolt, as if there's a bad connection somewhere in the wiring harness. Afterward, you can mainly feel that the car is vibrating.

Attached are images showing the values in both cold and hot states, along with a log file.

Was wäre, wenn der PD Kabelbaum, der für das "Aspirant"-Modell als Nummer 1 galt und bei dem es Probleme mit dem "Ruckeln" gab, durch ein neues Teil ersetzt worden wäre?

No, I haven't.
I recently had to buy a new one, but most of them work again if you slightly twist the connectors in the power distribution unit.

or maybe not... but for such a low price, it's always my first choice.

I've now installed a new old pressure differential element and new seals, and I've swapped the connectors of the pressure differential elements.
The strong jerking is gone, but it's still vibrating a bit, although that could also be coming from the dual-mass flywheel.

"3 Zylinder is still occasionally dropping to -65, but the cost of repair now exceeds its value."

I might have preferred to log the MWB018 instead of the 1, because of the wiring harness.