Zero compression on #4 cyl

That is odd. The only explanations I can think of is stuck valves ( but three our of 4 ), or a broken camshaft or chain/belt which I guess is possible, but then, it shouldn't run at all. Remove rocker cover and look inside. Zero compression is very odd.

You have to put compressed air into the cyl to hold the valves up (tool goes in place of spark plug)remove rocker cover ,remove cam, belt or chain !Put engine on TDC and mark valve timing dot,s on cam wheels so it goes back together the same , replace the seals one cyl. at a time,white out makes a good marker fo cam marks.

Hi do you know history of vehicle ? Has it had regular oil changes through out it's life, these engines do sludge up if not looked after. Try wet compression test 1st then rocker cover requires removal for no 4 cyl for diagnosis. 1st.Check for sludging , broken valve spring, or any other issues for no 4cyl. If sludging is pressent my advise is unless complete engine strip down and rebuild is carried out do not carry out repair. Chances are it wont last long. These engines completely rely on good oil circulation. A new engine or second hand engine would be advisable. If second hand remove a rocker cover and check for sludging before fitting. Also ensure the engine is correct for your vehicle or you may have ECU issues. In other words engine has to be removed again. Good luck.

Before starting first put engine on #1 TDC compression stroke. Adjust #1 rockers such that you have zero lift (push rod will spin by hand but just barely), then tighten additional 1/2 to 3/4 turn in 1/4 turn increments with time for lifter to pump down between turns. A shop manual will tell you which others you can set at this same time (I forget). Then rotate engine one full turn and set the rest. I like to then run engine until warm and while at idle and using clips that cover the hole in each rocker arm where oil squirts out, I loosen each rocker one at a time (engine running) until rocker starts to click, then in 1/4 turn increments I tighten them for final preload depending on what lifters I am using--some need 3/4 turns to center lifter, some need total 1 turn. All this will be found in any cheap shop manual.

It could be that the valve clearances need doing, if that doesn't fix it then put a oil pressure guage on it and check the pressure,

from autozone.com

ADJUSTMENT

22R and 22R-E
See Figures 3, 4, 5 and 6

1. Start the engine and warm it up to normal operating temperature.
2. Turn the engine OFF . Remove the air cleaner and housing, along with the hot air and cold air intake ducts.

CAUTION Components will be hot. The engine head, block and radiator will be very hot.

1. Remove any other hoses, cables, or wires attached to the valve cover. The valve cover (or cylinder head cover) is the domed steel item with the oil filler in it.
2. Remove the small nuts holding the valve cover, then lift the cover off. Retrieve the rubber gasket and put it aside; it can be reused if not damaged or crushed out of shape. Beware of hot oil dripping from the inside of the cover.
3. Use a large wrench on the crankshaft pulley bolt to turn the engine clockwise until the timing mark on the pulley to 0 on the scale. Turning the engine will be easier if the spark plugs are removed, but this is not required.

CAUTION Do not attempt to align the engine by using the ignition switch to turn the engine. Doing will splash hot oil onto everything in the area, including you.

1. Check that the rockers on No.1 cylinder are loose and the rockers on No.4 are under tension. (No.1 is closest to the radiator; No. 4 is closest to the firewall.) If this is true, the engine is aligned with No.1 piston at top dead center. If it is not true, turn the engine one full revolution clockwise and realign the timing mark at zero; recheck the rockers.
2. Adjust the clearance 0.008 in. (0.20mm) intake and 0.012 in. (0.30mm) exhaust. Insert a feeler gauge and check for proper clearance between the top of the valve stem and the bottom of the rocker arm on the No. 1 intake valve. To adjust, loosen the locknut on the end of the rocker arm and turn the adjusting screw until the clearance is correct. Tighten the locknut and recheck the clearance; there should be a slight drag felt when the feeler gauge is pulled through the gap. Repeat the procedure for No 1 exhaust, No 2 intake and No. 3 exhaust.

Fig. Fig. 3: Adjust the clearance of half the valves, do the arrowed ones first

Fig. Fig. 4: Use a gauge to measure the distance between the stem and the rocker arm

Fig. Fig. 5: Hold the adjusting screw in position, then tighten the locknut

1. Turn the crankshaft pulley one full rotation clockwise until the marks align at 0 and for the remaining valves.

Fig. Fig. 6: Adjust the second set of valves the same as the first

1. Clean the valve cover thoroughly with a lint-free rag. Wipe any oil off the cylinder head edges in the area of the valve cover gasket.
2. Fit the gasket into the valve cover, making sure it is not crimped or twisted. If the half-moon rubber plugs came out of the valve cover, clean them and apply sealant to the part of the plug contacting the valve cover; install the half-moon plug.

The use of sealants on the valve cover gasket is not recommended.

1. Install the valve cover onto the head. Make certain is squarely seated and not pinching any adjacent wires or cables.
2. Install the valve cover retaining nuts. Tighten them to 43-60 inch lbs. (5-7 Nm) This is little more than finger-tight; overtightening will deform the cover and cause leaks.
3. Connect the lines, hoses and cables which were removed for access. Make certain electrical and ignition wires are firmly held by their clips or brackets.
4. Install the air cleaner with the hoses and duct work.
5. If still in place, remove the wrench and socket from the crankshaft pulley.

Change your spark plug wires, I would have started with that first.


I’m happy to help further over the phone at https://www.6ya.com/expert/jeremy_69f3cc28d95bf514

Could be bad valve, or bad plug/plug-wire, maybe bad coil-pack but usually will be two and not just one as they are typically in pairs.  Crank-shaft positioning sensor may be dirty or piece missing from the flywheel or where sensor is meeting it. Injector may be bad!
Do compression test, if low pressure, put cap or two of oil in cylinder, re-test, if pressure goes up it's the rings, if not, it is a valve.
Bad rings on one or two cylinders is a sign of too much fuel, and this is hard on the catalytic converter.

theres this seal that go on the rocker arms rail
you need to remove the rocker arm rail
if your very good mechanicly try it

A leakdown test is where you remove the spark plug from the problematic cylinder,and install an adapter and air hose,shop air,about 90 to 120 psi.You have to be certain both valves are closed on that cylinder,and i do this by removing the valve cover on that bank,rotate the crankshaft and watch the rocker arms work on that cylinder,and watch them close completely.Now,install the shop air,and listen for air hissing in the tailpipe,this checks the exhaust valve,and then the intake manifold,this checks the intake valve.Now,you can also listen in the crankcase,and if you hear hissing in the crankcase,then you have bad rings,or a piston with a hole in it.