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04 Expedition, 5.4l 2v. Engine misses and shutters when under load, when in neutral it revs fine. Throws a code for cylinder misfire, but not always the same cylinder. Changed all the plugs, while doing that I noticed the EGR valve had a bad line on it so I replaced it as well. Still have the same problem though. Could the coils be going bad? Its a coil on plug ignition, so is it possible that I could have multiple coils bad at the same time?
 

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Misfires are usually coil related. I know it's too late now, but for future reference the easiest way to diagnose is it to put a code scanner on it. It'll tell you which cylinder(s) misfiring. Then you swap the coils from those cylinders to cylinders which are not misfiring. Then clear the misfire codes, drive it again until misfire codes show up again. Once they do, if the misfires move to the cylinders you swapped the coils over to... those coils are bad and need to be replaced. If the misfire does not follow the coils to their new location, the misfire is usually due to the spark plug.

One thing, never get water under the hood. Never take a hose sprayer under the hood. Clean only with non-water products. The reason being is the water seeps past the coil boots. Everything seems fine, but over time as the engine gets hot the collected water evaporates and then condenses inside the coil when the engine cools. The misfire then develops. And because it doesn't always happen for days or weeks, most people never connect it with the water under the hood. I am not saying this because you had water under the hood, but for future reference just so you know not to clean under the hood with water/water-based products.
 
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