I have replaced ALOT of spark plugs for similar issues.What helps me identify plugs as the problem is taking it out at highway speeds and flooring it,if plugs are bad it will repeatedly pop out of the intake,buck and jerk.Also when this happens the catalytic converters go bad due to unburned fuel going down the exhaust and superheating them.Is that 5300,or 53,000 miles? My customers usually argue the fact that it has 100,000 mile plugs,but we see them fail from 50-70k miles frequently.I would also suggest taking it to a Ford dealer or to a good independent shop tech because there is a certain way to get the plugs out without breaking them! Depending on how they break,extracting them is no fun,sometimes head removal is necessary.