This is the reason we usually recommend using OE manufacturer for plugs...in our case ngk which has a preset gap of 11mm or .43-.44 which is what is recommended for our engines <img src="/forums/images/graemlins/cheers.gif" alt="" />

Interestingly enough, there is conflicting information on Kia Tech Info.

If you look up the repair procedures under the Engine Electrical System/Ignition System/Spark Plug for the 2001 model year (and maybe others, too), at one point in the "installation" section it states that the gap should be 0.039-0.043. It also states this in the specifications.

But further down in the inspection section, it states the gap should be 0.028-0.031.

I saw a moderator on another Kia forum recommend .030, so I went with that for now. If I open it back up again at some point, maybe I'll gap it back up to .042 and see if it still runs smooth.

I'd imagine a smaller gap would run smooth, but not as powerful. A larger gap would be powerful moreso, but risking misfire or rougher run underload??? this is my guess. Anyway. Mitchel1 OnDemand at the shop I work at confirms .039-.043. I can also attest Londart's Credibility. He's our parts guy at the shop.

The correct gap is indeed 0.039 - 0.043 (1.0 - 1.1 mm). I would re-gap them back to the correct spec.

If the misfire returns and the replacement/swapping of the coil packs and plugs haven't fixed the issue it's time to look for other causes.

If you are finding oil on any of the plug threads replace the valve cover gasket. Perform a compression test on all the cylinders. They should be within 10% of each other.

Other possible causes: Bad fuel injector (not very common), cracked exhaust manifold (very common). To see if the manifold is cracked remove the heat shield surrounding the O2 sensor.

A trick I learned to check if you have micro cracks or a leak in the gasket for the exhaust or intake manifold is to spray carb cleaner or starting fluid (ether) in the area around the exhaust or intake manifold. It is highly advisable to do this when the engine is cold and just started. When it gets warm it works too, but you need to be careful not to use too much because you can cause a fire. Carb cleaner and ether are not as flammable as alcohol and will plug the crack for a second or two. This gives you enough time to see if it starts running smooth again.

Logansportage <img src="/forums/images/graemlins/patriot.gif" alt="" />

my xhaust mani is cracked, and has a small buildup of black around the crack, but it's been this way since I've owned it. runs great. Crack isn't big enough to cause any noticeable exhaust leak noise. (ie: pfft pfft pfft) ya know..