Hi,

This engine is a B23 and should have a anti knock sensor located on the left side of the block under the intake manifold. It looks round and flat with a screw in the middle.
The electrical connector is similar to the the throttle switch clips as I remember. I cannot say if they can be switched around or not. It's rare for the sensor to fail but connectors are subject to change without notice.

If you have a timing light it can be checked to see if it's working while the engine is running.
You take a small hammer a tap the engine block to simulate a ping and the computer will shift or jerk the timing mark around a couple degrees on each tap.

Low octane or if the engine burns a fair t lots of oil and is driven a lot around in town there could be excessive carbon build up.

The symptoms of piston slapshas already been discussed and changes with temperature and with B23 & the 230's. A tic could be valve lash, a clack is piston slap and ping is heard in the cabin under acceleration. Very seldom at idle, if ever.
B 23 and the turbo's helped invent the LH 1.0 systems to control spark knocks.

Combustion knock, that's closer to a diesel noise if there is a Coolant leak getting into a cylinder. The spark plug color will be very carbon free. Lots of steam back at the exhaust.

Read the plugs and observe the timing mark for erratic movement in case of a misfire.
These these are adjusted for very quickly with a bump in idle on all LH's but you do not say how it's idling.
A spark jumping to a ground spot will make tic tic sound regularly how old are the ignition wires?

Phil