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I just got the spark plugs changed because my 2009 6 cyl. Jeep Wrangler (with 70,000 mi) was throwing code for a misfire. After the change, it doesn't run as smoothly as before. It chugs and skips, but does not stall. There are no warning codes showing up currently.
Is this considered normal for a vehicle with newly changed spark plugs? If so, how long should I expect it to take until it runs smoothly again?
Your engine should run smoothly the second you change your spark plugs, smoother than before even, that's the whole point of replacing them. Otherwise, something else is wrong or was performed improperly.
Sounds to me like one of the spark plug wires isn't fully seated. I would check both ends of each cable and make sure they're fully seated.
The engine code it produced should give you some idea where to start:
If the code is P0300, it could be many things, but usually indicates a compound problem such as improper firing order or multiple unseated plug wires among others. If the error is cylinder specific, check that spark plug (the plug wires are usually numbered if you don't know which is which).
Facing the engine from the front:
1, 3, 5, are on the left, front to back.
2, 4, 6, are on the right, front to back.
If you find one that's improperly seated, check them all, just to be safe.
