Whenever you have a cylinder issue, start easy.
Easiest thing to do is make sure the coil wires are connected and the spark plug is snug. Check for vacuum leaks. Look over your hoses and electrical connections. Make sure everything looks fine. Go over it three times to make sure you didn't miss anything. If need be, get a picture and compare it.
If the problem persists then disconnect the fuel injector plug and coil wire one at a time to see if there is any change in idle. If there is no change then there is definitely an issue in that cylinder. So next easiest step is to look at the fuel injectors. Swap the injector of the problem cylinder over and see what happens. If the problem moves to the new cylinder then you know it was the injector. If the problem stays then you need to go to the next step. Now is when you swap the coil pack wire of the cylinder in trouble with the next coil pack wire. If the issue switches and follows the wire, then it is the wire that is giving you trouble. If the issue stays in the initial cylinder, then it is not a coil wire so move on to the spark plug. Simply remove the spark plug and check it for hair line cracks. Check the gap on it. If it looks fine, then swap it to the next cylinder like you did with the coil pack wire. If the problem switches to the next cylinder, then the plug was the problem, if not, then it wasn't the plugs and this is when I would start to worry a little. Now you want to check the coil packs. That is when you wanna swap/replace it and see if that was the issue all along.
If you get to that point and nothing solved the issue then you need to look deeper. Maybe the gasket on the IM port is bad. Maybe something is loose. It might be a good idea at that point to have it look at by a shop...and not someplace like AutoZone or PepBoys, lol!! Hopefully it won't be something like a mechanical issue on the engine or in the cylinder. Good luck with it.
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