TDI Jerking on Audi A6 C4 1.9 TDI

Hello,

'I'm experiencing the well-known TDI surging/jerking issue in my Audi (it starts around 3000 RPM). About 1.5 years ago, I replaced the mass airflow sensor (MAF), which improved things significantly, but the problem never completely disappeared. Today, I read in another forum that someone with the same car model is also experiencing this issue. In their case, various parts were replaced, including a solenoid valve. After replacing that valve, the surging stopped for them.'

Okay, and now to my question: Does anyone know which valve this is and where it's located?
My Audi is an A6 C4 1.9 TDI with 90 horsepower. The engine code is AHU and it has 125,000 kilometers on the odometer.

Thank you in advance.

Regards,
Michael.

There are many types of solenoid valves, but what I can imagine is...
The magnetic valve on the diesel pump (located on the front side, where the diesel lines are).
It's also possible that the needle lift solenoid is defective.

Hello,

I found the solenoid valve. It's the solenoid valve for boost pressure limitation or boost pressure regulation (I think that's what it's called). I replaced this one over the weekend, and my engine misfire is gone.
The valve cost 30 euros.
I just wanted to get that off my chest.

Regards,
Michael.

Then, please provide the number.

028 906 283 F

It is also called the N75 valve (there are already many threads about this), and it's a "boost pressure control solenoid valve."

I replaced mine because it was making a rattling noise when the car was stopped - the new one is quiet.

m;

PS: The device will never cause any jerking or swaying when it is turned on or off. It might produce some forceful movements, but there will be no jerking.

When the NHG (presumably a software or system) is no longer functioning correctly, it's more likely to produce errors and, above all, error messages.

A problem with the mass airflow sensor (MAF) would also have been a good candidate. I remember having a similar issue on an ASV once, where it would intermittently output 0 mg of air, which naturally caused the engine to drastically reduce the fuel injection amount. (unplug the connector, plug it back in, and everything was okay ).

Hello,

Here is the part number for the solenoid valve: 028 906 283 F.

'But after the change, the jerking is gone. It was most noticeable when I was driving on the highway and accelerating in fourth gear. Under full load in fifth gear, you could see in the headlight beam that, corresponding to the jerking, soot was being emitted. There was soot being emitted, then none, then some again, then none, and so on.'

Regards,
Michael.

MichaelM wrote:

Under full load in fifth gear, it was visible in the headlight beam that, corresponding to the jerking, soot was constantly being emitted. There was soot emission, then none, then some again, then none again, etc.

Hmm, that's interesting because the quantity control system on the soot reduction belt apparently doesn't (always) work perfectly...

@MichaelM: ...or is your engine somehow modified? That could certainly explain the tendency to produce soot.

Hello,

No, my engine isn't tuned, at least not yet. But I'm considering it. The A6 isn't exactly a lightweight. It has a 90hp AHU engine in the A6 C4, which isn't exactly overpowered.

Regards,
Michael.