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.

Apologies Tripper. Must've missed your other notifications. If you're getting a cylinder overtemp signal the computer is putting the engine into a type of "save" mode where the the cylinders alternately become air pumps by having the injector signals stopped. It helps keep the engine cool enough to hopefully not damage the aluminum heads but you'll lose mucho power. Also the cooling fans stay on & the A/C compressor clutch wont engage. I don't think the CHT code will be erased from memory by disconnecting the battery. Now I'm wondering if your getting some coolant leakage into one or more cylinders via the intake. Had that happen on cars & it would start running bad after the T-stat opened. Could also be a head gasket or head. Is the upper rad hose getting firm after reaching operating temp? Also if your using a tee when flushing, remove the T'stat & reinstall the housing before you do the flush or the T'stat will stay closed & the engine will not get flushed. Best way is a flushing tee [5/8" IIRC] in one of the heater hoses. Do that at least every other spring & put in a new T-stat. These cars are bad about the coolling system becoming electricaly charged, causing corrosion usually in the heater core. Ferd attributes it to improper flushing & the rust inside the system but we've had cars that start getting heater cores every 3 months. Not an easy, quick job. Maybe 1 out of 10 cars in our fleet will develop this problem. We put more heater cores than that but as far as repeats on the same car? That's reletively rare. Aslo I've seen the heater hose over #4 cylinder leaking onto the coil causing a misfire but that's usually constant once the coolant gets down in the coil boot bore. Aslo a misfiring coil can cause crazy things to happen. The electricity has to go somewhere & take the path of least resistance which is usually the engine ground. Well that ground is associated with all the other grounds & can make lights come on that shouldn't be as well as the power loss you're writing about.

That's some good advice. I have the tee spliced into my hose that goes into the heater core but I didn't think to remove then replace the thermostat. Ill do it again in a few days in the way you suggested. The light popped back on again today for like 10 seconds. I will give the upper radiator hose a feel and report back how it feels. Ill also check my #4 cylinder for leakage. If I don't find anything there what else could it be? I almost want to just replace every coil but that's a lot of money. Maybe ill just buy one and replace my #5 coil since it was the original problem.

Ok so I finally gave in and bought a new coil pack from autozone for $50. I made sure to surround the boot and connections with marine grade dielectric grease. Its been about a week and the cars is back to normal. All I can guess is before the car was still misfiring causing an overheat. Thanks for the help. Problem solved.

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

Term papers

I know, if you look back in the thread someone already said that, but my issue became an over heating problem which ended up being a result of the misfire.

I had a similar problem in mine. It was a cylinder misfire. What happened is the left valve cover started leaking oil on the back. It caused cylinder number 8 (which is the cylinder on the back of the block on the driver side) the boot swelled and let oil down in the space with the spark plug. Ended up taxing the coil pack too much and took it out. The misfire started on a rainy day for me as well. I have since then replaced all the boots and electrodes, and that coil pack. The problem hasn't arose since, and I was my motor about every month, and the problem still hasn't arose. If it is an oil leak, i would suggest adding Lucas Oil Stabalizer to your oil next time you change it and run it in there from now on. If it is a leak, that will seal it up. Hope this helped