Ignition woes

Hey all. I am driving a 4 cylinder 2003 Hyundai Sonata just at 130000 miles. The other day on the trip back home the car started shaking violently and the check engine light came on. I ran the code and it led me to a cylinder 1 misfire. Today I replaced my spark plugs, and wires. The number 1 plug had some deposits on it, but nothing that should cause a misfire. Now when the car is in idle there is a spark that jumps from the boot of one of the new wires to the grounding on the corresponding coil. I have never noticed this spark before changing the plugs and wires. It does this with either set of wires. I have a picture below where the spark is jumping from. The car has a noticeable drop in idle when it sparks.

Do I need to look into getting some new coils?

That coil is probably bad.

If the coil can’t transfer the energy from the plug wire to the spark plug thru the coil, the spark will find the next available ground.


So I could possibly switch the coils with one another, and if the spark follows I have found my culprit?



I swapped them and sure enough the spark followed. Is this cause for me to park the car until I get the new coil, or could I putt around in it for a few days. Changing the plugs made the code go away, and performance seems normal again.

If there’s a poor spark at that spark plug it could mean unburned fuel is entering the catalytic converter. And when that unburned fuel ignites in the catalytic converter it can melt the substrate.

I wouldn’t drive the vehicle until the coil is replaced.


Ahh good point. I don’t want to be driving a potential fire ball around.

It’s more about not ruining your expensive catalytic converter.

One more question. My vehicle has 2 coils. Should I replace them both at once?

One should be enough. I think if you look closely at the coil tower, you will find a crack in it. The coil itself is probably good if not for the crack. You could try to goop it up with a dielectric grease around the outside of the tower and inside of the boot and that may contain the voltage and stop the arc. This would just be temporary if you have to order a new coil and you need to use the vehicle in the meantime.

If the tower is not cracked, it could be a carbon trail prom previous arcs, clean off the carbon and goop it up with the dielectric grease and you will be OK. You can get the dielectric grease in little single use packets at most auto parts stores. It may say spark plug grease. Do not use the anti-seize for spark plugs, that comes in a similar packet. Look for the word Dielectric. Its usually a silicone grease but doesn’t have to be.

BTW, you should use the dielectric grease on the second coil as well as the new one. Dab a little on the insides of the spark plug boots or over the insulators of the spark plugs.

This makes me wonder if I damaged the coil when I was re installing it. I put in the new spark plugs without anti-seize after reading some tutorials on the internet. Spark plug job went fine, but I didn’t notice the spark from the coil until after putting them back on. It doesn’t seem like I could damage it, but who knows.

Anti-seize goes on the spark plug threads, it has nothing to do with the coil. Your choice to use it or not depends on the spark plug you chose. Some plugs come with an anti-seize plating and using anti-seize paste on them would be counter productive. If your plugs were not plated, then you should have used the anti-seize paste. What brand and type plug did you use?

The dielectric grease goes on the insides of the boots, I usually put it in with a Q-tip or put a thin coat on the outside of the spark plug porcelain insulator, or both. I goop up the towers on the coils pretty good though. Coil terminals are pretty rugged, they usually get cracked from multiple misfires or if the coil is dropped onto a hard surface.

My bad, I mean’t I did not use anti-seize on the plug threads. I’m not sure what the brand was, got them from my local parts store. I think they were Autolite or something similar. Autolites are what came out of the car, and honestly I don’t think they needed replacing, but I already had them…I had no issues installing the first one, so i decided against using it. Got my wording wrong. So if I over tightened the coils there is no chance of cracking them? I believe they are metal on metal, or those look like metal plates to me where the screws attach. I sure as heck didn’t reattach them as tight as they were originally!

I will get some dielectric grease though.

If they were Autolite plugs, then I think you should have used the anti-seize paste. Usually NGK and Denso are plated, Bosch are not. Champion was for awhile, you have to check the package.

The crack I am talking about is where the spark plug wire plugs into the coil, aka the tower. These usually crack for excessive heat from a serious misfire, although I guess if any water got in there and froze, it would crack it also. Thats another reason for using plenty of dielectric grease.

Here is where I am now.

Got a new ignition coil and that seemed to fix the spark problem. After everything gets heated up it seems to still be missing, but only at idle and while in drive or reverse. When driving it seems to be great. I have no engine code showing. What should I check next?

No negative waves, Moriarty.

A malfunctioning EGR system (valve, passages, etc.) can cause these symptoms. A code won’t be thrown until it gets pretty bad.

You know what. I lifted the hood and another coil is sparking now. What are the chances of that? Seems like something else is at foot!


Replace it and go on. Plastic gets brittle with age.

Make certain that the wires are firmly seated at both ends.