Be sure the spark plugs and spark plug wires are factory specification - what the manufacturer says to install. People install "better" parts according to advertisements and what the auto parts guy says, but the auto parts guy is NOT AN ENGINEER!

Listen to the advice of the manufacturer.

Then do a compression test on every cylinder. No point in going further if the engine itself needs to be rebuilt!

Next replace regular maintenance items per factory service manual instructions. Spark plugs, rotor, distributor, air/fuel filters, change oil, etc.

And then do a fuel pressure test and fuel system internal leak test.

Check battery voltage and charging system.

Check for vacuum leaks.

That should solve most common problems. After that if still having problems, start checking individual things per factory service manual instructions. Don't guess, test these things as directed.

If you don't know how to do these things, take it to a mechanic. Throwing parts at a problem (replacing parts just guessing) can cause MORE problems! Parts may be wrong or improperly installed.