Terracan knocking combustion pre ignition

Hey, I also own a Terracan, though I've not had those exact symptoms. Knocking combustion can be caused by several things, but deposits in the combustion chamber are a common culprit. This can lead to pre-ignition, where the fuel-air mixture ignites before the spark plug fires. Have you checked your cylinder heads for excessive carbon build-up? Also, when was the last time you adjusted your ignition timing? Piston slap could also cause a knocking sound, but that usually doesn't cause smoke.

Thanks for the quick reply! I haven't checked the cylinder heads myself, nor have I touched the ignition timing. How difficult is it to check the cylinder heads for carbon build-up? Is that something I can do myself, or does it require special tools or expertise?

Checking the cylinder heads involves removing them, which is quite a bit of work, and you'll need new gaskets when you put them back. It's probably best to have a workshop do it, especially if you're not familiar with engine tuning. They can also check the ignition timing and see if that's off. Tell them you suspect deposits in the combustion chamber; they might have a camera to look inside without disassembling everything. If it is deposits, they might suggest something like an engine decarbonizing treatment.

Okay, thanks for the advice! I took it to a workshop, and you were right - it was deposits in the combustion chamber causing pre-ignition. They cleaned everything up, adjusted the ignition timing, and it's running much better now. The total repair cost was 425€. Thanks again for pointing me in the right direction!