Car was parked for two year, change oils, filter and spark plug but have knocking sound when start. what is the cause?

Yes it'd be a good idea to go ahead and change the oil and filter. And the fuel filter and put some fresh gas in it if they are easy to get to go ahead and change the spark plugs and check the wires. If it runs before you drive it i would change the transmission filter and fluid and Check the belts and make sure they are not cracked.

Is it metalling sound ? if that's the case then don't drive it .. you might be having issues with connecting rod or the bearings in the both cases engine will seize. Consult a auto technician, but you wont have engine light on due to this.

If it is knocking due to misfire (which is mostly the case as the engine light is also on) .... than find which cylinder have the issue then clean or replace the spark plug. If you can get a scanner to read the car computer it will solve the issue in a blink. Otherwise start the engine ... open the hood .pull out spark plug connector one by one and notice the change in sound... the one that is bad will have no effect on the sound.

Did this happen after changing spark plugs ?
Incorrect spark plugs can cause this.
Maybe the timings are wrong the gasoline is expoding before the piston reaches the upper position.

Oil change 5W/30 and Wynn's thin oil in crankcase . One bottle injector cleaner .to Gas tank .

I would do an oil change first and double check to make sure the oil is always at top level without over filling it. If the problem persists after that, then check your air filter, fuel filter and spark system.

Black smoke is usually caused by a bad oil seal, clogged air filter or fuel problem.

I am sure you have checked the oil. I would change the oil to start with. This sounds like a main bearing problem but if it did not knock when you parked it then I would change oil and if the knock persists have your oil pressure checked that will also give a clue to a main bearing problem.

Sounds af if you may have a transmission issue. I would take it to dealer to have it checked. Noises can be hard to track down even if you are standing next to a vehicle unless you have proper training in vehicle drivability

Sounds like misfire. Change spark plugs, wires, cap, rotor , fuel and air filters. Check for oil in spark plug holes. if oil found change valve cover gasket spark plug orings. they can leak oil into spark plug holes and cause misfire.

Joe ASE Master Tech

Where is the oil going? Is there evidence of leakage on the ground after parking overnight? My guess is that the garage did not tighten the drain plug or oil filter properly, causing it to leak out.
A knocking noise indicates serious damage to the engine, due to insufficient lubrication. The noise u hear is probably a bad crankshaft or connecting rod bearing. If this was due to improper tightening of the drain plug or filter, the garage is responsible (but good luck trying to get them to fix it). This is why I never let anyone change my oil/filter.