Gas in the oil pan?

Hi Aadil:
The spark plug that is misfiring should tell the story. Is it oil fouled? Bad rings or valve seal. Is it carbon fouled? Electrodes fried? Wet looking? Maybe a bad plug wire and it's not firing properly?
What kind of engine?
See if you can isolate the problem and we'll try to be more specific with help.

What you are probably experiencing is oil fouling of the plug due to valve stem seal wear. GM engines drain oil from the heads at the rear of the engine, so the #3 and #6 cylinders are most prone to this problem as oil will pool there on its return to the oil pan. The only solution is to replace the valve stem seals, but, knowing this is not a serious issue unless the oil fouling is excessive, you can simply clean the plug or swap it out periodically until engine rebuild is warranted.

run the fault codes to check for sensor problems that is causing this result.

What engine do you have? is check engine light on? You said you changed coil pack, but what about spark plugs? could be fouled by normal wear, improper application/plug gap, oil fouling (oil residue on electrode) caused by bad valve guide seals or bad piston rings or gas fouling(electrode wet with gas) caused by bad plug, wire, injector, O-2 sensor. Could be caused by a vacuum leak (hose or intake manifold/gasket) Check all vacuum hoses for cracking/chaffing, repair as needed. with engine idling spray carburetor cleaner at base of intake manifold watch for rpm increase if so there is a vacuum leak. Could be stuck open egr valve, Could be compression problem or timing chain problem. This is the best I can do with info you provided. Hope it helps.

was the gumout for gas or oil they look simular other than that make sure you havent fouled your plugs pull them take a good look if wet or soaked get new ones and try it also you may want to take out all your plugs and turn it over to see if your getting to much fuel You may want to change the fuel filter first just to put that out of mind its usually the simple things fuel filter makes the most sense

are any of the other plugs wet if not i would go to the junk yard and get 2 used injectors i doubt it did anything to converter if other plugs are wet to i'd say you need a new fuel rail and injectors kerosene probley melted or plugged the rubber inside put lots of gas in it to delute kerosene not just 5 gal and maybe a bottle of drygas kerosene sometimes has water in it

What kind of wet? Is the wetness gas, oil, or water? There are different types of fouling possible with reading the color of the old plug being a good indicator. Is the compression within limits?

Check your intake manifold by taking it off and comparing the ports going into the head. If the intake port on #4 cylinder is wet there may be a problem in the Intake. You will also be able to look at the intake valve stems on most motors. The newer designs have the water going into the block directly so the Intake contains no water.

You could have a bad oil seal on the valve stem. You could have a head gasket leak. Even some oil rings can still sling oil and if the power rings are good, it still will compress and give good readings.

You need to run the motor again and try wiping the plug again to see what kind of deposit is on it.

Odds are the fuel is stale. Gas turns if it is sat for a lengthy period of time. I would suggest :Drain the fuel tank, Take a 5 gallon can of gas. STP makes a product called (Ithink the makes is )Stihl.
It is a bottle you can see a red liquid in. It has a small measuring cup built into the top of the bottle.
Add the recommended amount to the 5 gallons of gas. Replace the fuel filter and if the plugs have not fouled, it should light right off. I'd suggest changing the oil and filter as well.
Good luck

SMOKING COMING FROM OIL SPILLED ON THE ENGINE AND MANIFOLD WHEN YOU CHANGED VALVE COVERS.OIL PROBABLY GOT IN PLUGS HOLES FOULING OUT PLUGS. SPRAY PLUGS WITH CARB CLEANER OR BRAKE CLEANER TO CLEAN THEM.DRY THEM. REINSTALL PLUGS BACK IN THE ENGINE.CLEAN OIL OFF ENGINE AND MANIFOLD SO IT WONT SMOKE. CRANK ENGINE SHOULD BE OKAY.

Perhaps injectors leaking by when engine off.