How do I correct "cylinder 4 misfire" code and check compression?

How long since a tune-up? Any applicable trouble codes? Some of the national brand auto stores will check po codes for free.
If a cylinder misfire, hopefully the code will tell you which cylinder, then check spark--fuel--compression on that cylinder. If a po300 code, that is a fault that is common to all cylinders, not just one.

If the misfire is on one a particular cylinder or perhaps 2, these issues need to be addressed and checked...
1. Power to the spark plug.
2. Coils and spark plug condition.
3. Fuel supply to the cylinder
4. Air supply to the cylinder
5. Correct fuel/ air mixture to the cylinder
6. Cylinder compression. Low compression or a cylinder compression level below spec will result in a misfire. If the compression tester shows low compression in a cylinder the causes of the poor compression reading then need to be addressed.

The fault codes generated by the computer and read by an appropriate scanner will tell you which cylinder or cylinders are misfiring.

94 gas engine? which one, (SIZE:?) and cylinder count.? 4?
this is called MISfire, AND IS caused by many things.
in gear what is in gear, the auto or stick trans, I cant guess that either.
Is this EFI fueling or in some far way country with old CARB?
we stopped carbs here about 1988. so... cant guess this either.
sure post country, that really helps, 1 in 100,000 hit rate on that.

sure bad spark is #1 cause of misfire! "a full tunejup"
but you skipped filters? (listed first, in tuneup list")
#2 on old engines like this is bad compression. 1 or more cyl.
#3 is bad fueling. (it can misfire flooding, or bog too lean)
too lean can misfire too,

i cant drive your car ,nor experience all modes of misfire.
so my answers will be all wrong, and wild guessing.
but Ill skip the guessing, ok 1 more, EGR leaks (that too is listed on the tuneup schedule as check EGR !)
i do the full tune up
it runs bad. still
i check spark timing , if way off the cam belt slipped....
5min. work that. just 5min. and omg wow;d timing jump 20 degrees retarded.?

i then check compression, it's and old engine, why skip this.?
the compression test is done wide open throttle, and will show
you if the engine even has some life left, say you get 170psi warm on all 4, and is spec. look like engine has future, so Ill invest repairs
if not , consider selling it (1hr work and speaks volumes on what to do next ,see?)
ok compression at spec.
now we have fueling,
you cant burn fuel with bad spark or bad compression so we arrive at fuelling, (complex)
ill stop here until you answer engine type, and fueling system
carb or EFI.
(3 possible diagnosis paths, carb, or speed or Air density EFI

tell more get more.

do the 60k tuneup or 100k, mile. per the book. fuel filter 20 yearsold?

You are misfiring. If you have Autozone (or similar) research your check engine light, they will come up with one or more of the following codes P0300, P0301, P0302, P0303, P0304 etc. etc.P0308. The P0300 code refers to "Random/Multiple misfires" whereas the other codes refer to that particular cylinder (last digit) misfire. The P0300 code sets when 2 or more cylinders misfire (can be the same 2 over and over, but it takes at least 2 cylinders to misifre to set that code. The others only take one misfire to set the code. Now that you know what is happening, here is how to fix....
Takes all to fire a cylinder (Fuel, Spark, Air & Timing) properly. If you have random or multiple misfires, it is likely something that is COMMON to all cylinders - like the air intake/throttle body area - throttle body can get carbon buildup and not open/close properly. Check the fuel pressure to the fuel rail(s), fuel filter clogged? When you turn your key to the "ON" position, do you hear the fuel pump turn on (whine) and then shut off? No whine, means no fuel pump. Check all fuses and fuse relays related to the fuel delivery system. Check the distributor cap/rotor for any signs of carbon tracking/arcing. Do you have good spark from coil? Check wiring for the Camshaft Position Sensor/Crankshaft position Sensor for timing issues. Finally, check compression on all cylinders. Need good compression for combustion to take place.

For a single cylinder (example Cylinder #2) - Easiest to check is spark. Pull the plug and look at it. Is it wet and smell like fuel? If so, then swap it with cylinder next to it. If the problem moved, then its the plug. If the misfire is still on Cylinder #2, then swap the plug wire (both ends). If the misfire is still on Cylinder #2, then swap the coil. (see where this is going?) If the plug is dry, then check the fuel injector for operation. Noid light tester or you can get a long screwdriver and stick one end on your ear and the other on the injector - it should make a steady, rhythmic clicking sound if it is functional when car is running. No sound? Replace. Is the plug oily? Check cylinder #2 for compression. No compression or little compression means either head gasket blown or bad/sticking valve (intake or exhaust) = big money to get fixed. Timing on one cylinder is hard to test without correct test tools. Timing is likely not a problem on a single cylinder misfire. Good luck.

need to have the dist cap checked they may have cracked it when they was installing the wires & or may have cracked plug when installing them

codes p 0300 is random misfires and codes p0301,2,3,4,5,6,7,8 are the cylinders that are misfiring
so un you statement the problem cylinders are 1 and 2
misfires are normally problem injectors and low fuel pressures so have the fuel pressure checked to make sure that the pump is running correctly, the pressure regulator is operating correctly ans the EVAP system is venting the tank correctly
use a couple of injector cleaner in the tank to clean the injectors

no heavy oil not going to help misfire. if you have a cylinder misfiring it has to be plug,plug wire,coil ,dist.cap &rotor,vavle,or piston rings ,an sometimes it can be headgasket . what u need to do is a compression check on all cylinders to compare to rest of them & do a leak down test on each cylinder only if the compression test are all the same psi. on all cylinders if u do this you will find the cause of the miss fire .

could be a burned valve. Did you do a compression test? What was the code specifically, P0303?

Have you replaced the plugs and wires recently or are they originals?
be sure you dont have basic worn out tune up parts before you start chasing major engine conditions...like... when was this car last tuned...does it have a dist. cap and rotor?? if so are they old parts as well??
If all is ok compression test the engine it may have a burnt valve or out of adjustment rocker arm etc.?

well i had a 98 dodge neon that seems like it did the same and it said engine misfire and all i did was due a tune up change spark plugs and wires.