I was driving in the rain, now my engine vibrates.
 

I was driving on the highway in the rain 2 days ago and about 10 miles in I felt this slight vibration in my engine. I though nothing of it until 5 minutes later my check engine light started flashing then would stay on, then flash, then stay on. I could feel a loss of power when i floor the car and now it is idling erratically. I have a feeling it's a piston misfire. Does anyone know what steps I can take to solve this. Also I heard my car might have coil packs and one might of just gotten wet. Maybe it just needs to dry or maybe I have to replace it. Any insight into this would be greatly appreciated. Thanks.

2002 Grand Marquis 4.6 v8.

Anyone?

OK well I unhooked the battery and when I reconnected it the check engine light went off. The car seems to be running better but I think there still is a misfire. Before I unhooked the battery I had autozone check the engine code and they said the #5 cylinder was mis-firing. So ill keep trying until I get a response or solve it.

The c.o.p system is bad about water intrusion. Pull the coils & look down in the holes they go in. You probably have water in one or more holes & it's making the secondary voltage arc before making it to the spark plug. Some silicone grease around the upper part of the boots where they attach to the couls will help prevent that. I put some on the inside of the hole where the coil goes in the boot as well.

When the CEL flashes it means there is a catalyst damaging misfire taking place

I'm having trouble finding the coils specifically the #5 piston coil. Do you know a link or a picture I could use for reference?

Front of motor ^^^

5 1
6 2
7 3
8 4



You can also swap the suspect coil with another coil on the engine & see if your misfire code changes cylinders. I get you have a #5 misfire. Those are right under the air intake tube & the wires for the coil connector can get pinched by the tube. You'll see when you take off the tube. Check the connector wires good to make sure you don't have a pinched or broken wire. I've only seen one but have heard of others where the wires were bad.

Nick thanks for your help. I was able to get to the coil. I cleaned it off and replaced the spark plug. I unhooked the battery to reset the computer. The car runs fine with lots of power until the car warms up. As soon as the thermostat opens the car will stutter for a second and then from that point on the over heat lamp will turn on for a second, lose power then go away. All my fluids are good, I'm getting heat in the car so I know the anti-freeze is circulating. I have no idea why this is happening now. I didn't even touch anything related to the cooling system. Any thoughts?

Ok well in the mean time I'm going to flush my coolent out and replace it. Hopefully that will help. Still not sure if this is related to my original problem.

UPDATE: I flushed out my coolent system and there was a lot of rust in the system. It took me about an hour just to throughly clean out all the rust in the over flow tank. I drove on the highway for about 20 milles (much longer then it took for the problem to come up) and everything ran fine. No over heat lamp but still a slight vibration in idle. I'll try replacing the rest of the spark plugs and see if that helps. Hopefully this thread can help someone with a similiar problem.