Get a cooling system pressure tester from the loaner-tools program at a local parts store. Pressurize the cooling system overnight, remove all the spark plugs. Look for coolant leaks--puddles on the ground, coolant run-off of engine components. Pull engine oil drain plug, look for coolant running out before the oil comes out. (no need to drain oil completely unless it needs to be changed anyway--or there was coolant in it. Reinstall drain plug, add oil (and filter) as needed. Then, pull the power wire off of the ignition coil, to disable the ignition system. Crank engine. See if coolant shoots out of any cylinders, especially #4.
Fix as required.
...and verify cranking compression on #4 at least, but all of them in general. Have the throttle open somewhat when performing compression test.
Then reinstall spark plugs. Reconnect power wire to ignition coil.
Note that the fuel injection "spider" system is a known trouble source.