Re: 03 navigator rough idle at stops
A vacuum leak is rare on them. To check a coil pack, you can umplug one injector at a time and see which on doesn't make a change, then switch it with another one and se if it move to the new location. If it's in a hard to get to location, move it to an easier place. See if the miss moves with it. You can usually feel a miss just setting there and not in gear. Also look at the rubber boots to make sure they aren't cracked causing a spark jump. When you change the plugs, make sure you use anti-sieze and a torque wrench. too tight and the cyl. head exands and pulls them out. If you have 5.4, be very careful, the plugs sometimes brek and special tools are needed.