Misfires Under Load - Needle Valve Issues?

Hello!

This topic has probably been discussed many times before, but I'm still particularly interested in it given my specific situation.
The car is an Audi 80 B4 1.9 TDI with 90 horsepower. In fifth gear, at a speed of approximately 160 km/h (about 99 mph), there is sometimes a brief hesitation or stutter (this happens occasionally, perhaps 3-5 times over a distance of 500 km).

I've read about the needle hydroshocker (NHG) several times now. Are these symptoms indicative of a faulty NHG?

If so, are these interruptions permanently damaging to the engine, or how quickly should the NHG (presumably a type of filter or component) be replaced?

Or are there other possible reasons why these interruptions might occur?

Markus.

Hello,

'I experienced similar symptoms in my Golf 3 TDI when the fuel filter was clogged. You could see it in the transparent hose connecting the filter to the pump; there was an unusually large amount of air being drawn through it. Initially, this manifested as occasional power loss during highway driving at higher speeds. After a few days, the engine only ran smoothly in the lower and mid-RPM range.'
Regards,

Eike.

Hello!

In my case, it's been happening for about half a year now! So far, it hasn't actually gotten any worse.
I'll definitely take a look at the fuel filter.

Markus.

The symptom sounds like a faulty needle lift solenoid. You can easily check it this way:

Bring the engine up to 3000 RPM.
Gently tap the nozzle with an object, using the NHB (which is the one with the cable).
If the NHB (negative high-voltage breaker) is defective, the engine will start to misfire; otherwise, it will continue to run normally.

Basically, a faulty NHB (needle valve body) won't damage the engine itself; it just means it's not injecting the correct amount of fuel, which you'll probably notice through a loss of power. You can buy a replacement injector with an NHB from Beru or Bosch for around 145 euros, and you can easily replace it yourself.

best regards

Hannes.