After an expensive repair and other fine-tuning stuff, it was time for
timing adjustment.

- 2250RPM, unplugged the Temp Sender, and turned the distributor left
and right a couple of times to get it perfect. At one of those turns
(probably more than needed), a puff of white smoke came out and the
loudest engine knocking noise I've ever heard. Turned off the engine
right away and took a big breath.

-put the key in and tried again. Engine was running fine without any
smoke or anything but the same very loud knocking noise. Broke our
hearts! Thought I did something huge ... pistons, bearings... or who
knows what!

-disconnected battery +, disconnected ECU, walked away ... came back and
connected them back again.

-started the engine and could still hear a very silent low noise

-decided to take it out of the driveway

-as soon as I got out of the driveway, the noise completely disappeared

-drove around and no problem. As a matter of fact, it drives the
smoothest ever!

The van hadn't moved for more than a month because of repairs
(alternator burned, and so did ECU). Apparently, rotating the
distributor caused something. I am thinking that it messed up the ECU.
For a moment I thought that the engine was all messed up. Also, a few
years ago, I heard a very low deep knocking noise that was not of major
concern. I replaced the Fram oil filter with a VW one and the noise went
away.

Questions:

What happened?

Low oil pressure?

Would the oil filter do something like that?

We are not going to have engine problems now, are we?