Golf 3 Idle Control Valve: Troubleshooting Jerky Engine

Hello,
My TDI, which admittedly isn't exactly new anymore, is experiencing irregular jolting during steady highway driving. Previously, this only occurred under heavy load (around 160 km/h), but now it happens more frequently even at 120-130 km/h. After some jolting, it eventually stops for a while, until it suddenly starts again.

I once read somewhere that this could be due to a needle injection pump. This pump is supposedly located on the 2nd cylinder and can allegedly be removed, as newer TDIs no longer require such a system.
But what happens if you simply disconnect the connector? Does the engine continue to run normally, or does it switch to a limp mode, or does it stop altogether, or...?

I would really appreciate any tips. Best regards,
Jürgen.

Hello,

I wouldn't simply disable the needle lift compensator.
Did you read the error codes? If so, please post the results here.

Another possible cause could be the electromechanical control valve. You can find some posts about this issue in the forum.
Just search for it...

j.stupperich wrote:

Somewhere, I once read that it could be due to a needle injection pump.

This is supposedly located on the 2nd cylinder and can allegedly be disconnected, as the newer TDIs do not require such a system. }

Hi.

In a way, the "rumor" is true: the newer PD engines fundamentally no longer have a needle lift device (NLD).
That doesn't mean that you can disconnect the connection to the NOx sensor on older TDIs without consequences; as far as I know, it will always result in a noticeable loss of power (limp mode).

For a DIY test, have an assistant bring the engine up to approximately 3000 rpm while it's stationary, and then tap on the longer fuel injector (where the NHG valve is located) with a tool. If the engine stutters in response, the NHG valve is defective --> replace the NHG injector.

Hello Jürgen!

'I experienced exactly the same symptoms with my car, from a mileage of 66,000 to 110,000 kilometers. Back then, I specifically contacted VAG (unfortunately, this forum didn't exist yet in 1999).'

The needle lift actuator and the boost pressure limiting valve were both replaced.

Since then (now at 206,000 km), everything has been quiet.

Best regards, D.