TDI: The Ultimate Guide

Hello everyone,

'My VW Passat 1.9 TDI (engine code: 1Z, year: 1995) is making a knocking sound, as if the hydraulic lifters are defective. I've already replaced the cylinder head with the camshaft and lifters, but it hasn't made any noticeable difference. The engine starts without any problems and doesn't have any loss of power while driving. There's no smoke and the error memory is also empty.'
I'm at my wit's end; who can help me?

Check the injection pump's start of injection! If the injection timing is too early, a TDI engine will make a significant knocking noise...
Possibly, the pump is misadjusted!

How old are the nozzles?

The injectors are about 6 years old, but I had them tested by a Bosch service today. The spray pattern and injector opening pressure (185 - 195 bar) were okay. Tomorrow, I'm going to try swapping the injectors with a set from another Passat 1.9 TDI (same model, same engine) and see if there's any difference.

Just check the start of the injection process first; it's a 5-minute thing, including booting up the laptop.

We checked and readjusted the injection system yesterday. At the same time, I noticed that the engine runs smoothly from approximately 2300 RPM. Even a friend who works at the dealership doesn't have any answers.