Hey guys and girls on this site. This is my 1st post here.

This weekend me and my father went camping and took his 2004 expidition to tow his 28 foot trailer and on the ride down to the camp ground my father's truck ran great. We were going down the interstate passing other people left and right having lots of fun until the next day we left our trailer driving to a place in the state park and the trucks check engine lite came on and was blinking if we went above a certain speed and the truck wasn't running Normal and we checked it out and noticed his muffler poped a hole where it was welede before so that night we ran to auto zone and bought something to patch it but that didn't solve the problem. So the today we ran to auto zone again and asked the worker if they could use a reader to check the error code. The code said the 4th plug was fouled.

Then we left the campground and noticed on the way home the truck started running smoother and the check engine light is not blinking anymore but was still there.

We were wondering could the muffler leaking caused the plug become dirty and running the truck harder cleaned it?

Also for the check engine light. If the plug got cleaned will the check engine light go away or will my father need it to he cleared? My father has a tester but it doesn't work with on his truck.

Also to mention my father mentioned he had that plug replaced about a year ago

 

We need the specific code that popped. Either p0304 or p0354 for your misfire. Was there any others with it? If it was blinking that is the pcm telling you that there is possible damage occuring to your catalytic converters due to unburnt fuel in your exhaust system. To check this without just throwing parts at it you should invest in a hei spark tester. Check that specific coil. If that checks out then test your injector. I would venture to say your coil is possibly bad. And yes you should get the hold in your exhaust welded up. If you don't have a welder any muffler shop will do it for under 20 bucks just make sure they disconnect the battery before any welding is done. Oh, and if you want to clear the codes and computer to double check the code, disconnect the battery and turn on your headlights for 15-20 min that will clear out any previous codes that were tripped. Let is know where your at after you check your coil. Btw the cylinders are 1-4 on left side and 5-8 right side if your looking at engine from radiator back. Comprende?