GIII Knock Sensor, AHU 90HP, 260k km

Hi,
I drive a Golf III with an AHU engine, 90 horsepower, and 260,000 kilometers on the odometer.
"I have an interesting question that no one has been able to answer for me. When the engine is cold or warm and running without a load (e.g., in 3rd gear), and I give it a little gas, I hear a slight knocking sound. When the engine is under load, the sound disappears. I suspected it might be the lifters, but replacing them didn't solve the problem. The sound is a bit more noticeable when the engine is cold."

Thank you.
Paul.

Hi Paul,

It could also be the fuel injectors or connecting rod bearings. If the injectors are still the originals at 260,000 km and you plan to keep the car for longer, you should replace them and have them adjusted (i.e., have the injector nozzles replaced in the injector holder).
Connecting rod bearing: Remove the oil pan and shake it. Yes, it's a tedious job, but if the connecting rod pin is already damaged, it's too late.
Basically, that knocking sound could be caused by all sorts of things, so I don't want to immediately scare you by suggesting it's one of the more serious possibilities. It's hard to judge from a distance.

Best regards, Rainer.

Thank you for the ideas.
My suspicion is related to the nozzles. As far as I know, they haven't been replaced yet, and the machine is producing a bit of black smoke. I wasn't sure if this symptom could be caused by the nozzles. However, my technical intuition points more towards the connecting rod bearings.

Hello.

pandabear wrote:

When the engine is cold or warm and running without a load (e.g., in 3rd gear), and I give it a little gas, there's a slight knocking sound. When it's under load, it goes away. Bitte gib mir den deutschen Text, den du übersetzt haben möchtest. My technical intuition, however, points more towards the connecting rod bearings.

Hmm, connecting rods that only make a ticking noise under light load, regardless of whether the engine is cold or warm, would be very unusual, in my opinion.
Do connecting rods become louder as the oil becomes thinner or as the engine gets hotter?

I'm also suspecting the old injectors. The combustion in a TDI engine can sometimes make the strangest noises...

I've only observed that fresh oil makes it a little better. Certainly, several factors could be contributing. I noticed this slight knocking even at 210,000 km (when I bought the Golf), but it was a bit less pronounced. Of course, I have to say that it's nowhere near a serious knocking sound. I'm an engineer, and I have a keen ear.
Regards,
P.