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2006 300c Spark Plug issue

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3K views 16 replies 7 participants last post by  Lysol106 
#1 ·
Well, standard maintenance just took a bad turn. I literally just pulled the first cylinder on the driver side and was greeted by this.

The metal prong on the spark plug is completely gone. So my question is, how bad is this? Im not going to be able to pull the head and I don't have a scope to look down in the cylinder. Has this happened to anyone else? Trying to think through some options before my head goes to the absolute worst possible scenarios.

Thanks!


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#6 ·
It was running pretty well. It would have a weird stumble/miss at a spot in the powerband and in 5th gear. It did idle a little rough today, which made me realize I needed to change the plugs.

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I'd change them and see what the car does. No sense in pulling the head and seeing something that's not gonna be there. I'd start there for sure. I've seen that happen before a time or two at the shop.

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#13 · (Edited)
IMHO, if you had a major issue like a dropped valve seat, you would already know you had a massive problem. Trust me, been there.

The fact that the other plug is intact suggests no dropped seat, otherwise it would be mashed to heck.
Bad gas at one point starting detonation or pre-ignition combined with lack of maintenance (or vice-versa) can cause this.

Question for others on the coil pack... is there only a single secondary high voltage winging as in all other dual plug, single coil applications that I have ever worked on? If so, the plugs will use each other for a "ground" to complete a circuit. One bad firing plug would be unrelated to coil condition in that case (both would fire poorly).
: EDIT : I just checked a coil pack and see three primary wires and the two exposed secondary coil points do not have continuity.
Suggests to me that the coils indeed are separate for each plug (allowing much greater control for staggered timing to plugs - neat).
Therefore i've blown my own theory of one pack affecting both plugs out of the water.

Your coil is likely : EDIT : "potentially" fine, just the rubber boot abused on that side by the ever increasing gap it had to fire across and hot as heck.
There is a "spring" that sits within each rubber boot that connects the end of the spark plug with the coil, i've had these drop out, so keep an eye out.
This may also have been damaged by any "arcing" between the spring and plug.
Gas Wood Machine Auto part Cylinder


If it were my engine (with your description of how it was running) I'd replace all plugs, re-use the coil and see how it runs. Of course, look at all other maintenance items that have been left too long!!!

For what it's worth, I have previously replaced ALL coil packs based on questionable advise from "the internet" that made no difference at all, other than a lighter pocket. The coil packs are relatively simple and rugged and rarely an issue, much like an old school model T Ford coil pack. Any "smarts" are handled by ECU. I may be wrong, but perhaps a Chrysler tech could tell you how many genuinely "bad" coil packs they have replaced in their career.

I hope that my 2 cents helps a little.
As far as GOOD ADVICE goes, this is an awesome group that will chip in here and steer you right.

Good luck.

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#14 ·
IMHO, if you had a major issue like a dropped valve seat, you would already know you had a massive problem. Trust me, been there.

The fact that the other plug is intact suggests no dropped seat, otherwise it would be mashed to heck.
Bad gas at one point starting detonation or pre-ignition combined with lack of maintenance (or vice-versa) can cause this.

Question for others on the coil pack... is there only a single secondary high voltage winging as in all other dual plug, single coil applications that I have ever worked on? If so, the plugs will use each other for a "ground" to complete a circuit. One bad firing plug would be unrelated to coil condition in that case (both would fire poorly).
: EDIT : I just checked a coil pack and see three primary wires and the two exposed secondary coil points do not have continuity.
Suggests to me that the coils indeed are separate for each plug (allowing much greater control for staggered timing to plugs - neat).
Therefore i've blown my own theory of one pack affecting both plugs out of the water.

Your coil is likely : EDIT : "potentially" fine, just the rubber boot abused on that side by the ever increasing gap it had to fire across and hot as heck.
There is a "spring" that sits within each rubber boot that connects the end of the spark plug with the coil, i've had these drop out, so keep an eye out.
This may also have been damaged by any "arcing" between the spring and plug.
View attachment 62827

If it were my engine (with your description of how it was running) I'd replace all plugs, re-use the coil and see how it runs. Of course, look at all other maintenance items that have been left too long!!!

For what it's worth, I have previously replaced ALL coil packs based on questionable advise from "the internet" that made no difference at all, other than a lighter pocket. The coil packs are relatively simple and rugged and rarely an issue, much like an old school model T Ford coil pack. Any "smarts" are handled by ECU. I may be wrong, but perhaps a Chrysler tech could tell you how many genuinely "bad" coil packs they have replaced in their career.

I hope that my 2 cents helps a little.
As far as GOOD ADVICE goes, this is an awesome group that will chip in here and steer you right.

Good luck.

Sent from my SM-G955W using Scat Pack Forums mobile app
To answer the tech question/portion of this comment, the Hemi coil packs I'd say 1 out of every 30 coil packs go back. It's for sure not a common issue. I put more coil packs on the 3.6l penastar engines here as of late. However with the hemis, if you run the plugs too long they will start to use to boots to arc against the cylinder head to try and find a path to ground. The coil pack itself does have 3 pins, however the PCM only uses/needs 2 pins. ASD powers one pin and the PCM controls the ground to fire the plugs simultaneously. I personally wouldn't re-use that coil pack, it's far too gone. I'd replace that single one, replace the plugs on the motor, reset the PCM clearing all of the adaptives and run it down the road. See what happens.

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#15 ·
Thanks for all of the insight. My parents had the 300 towed to a local performance shop. He's going to look down into the engine with a boroscope and see what the damage is in the motor. Luckily I have a seat of Eagle Heads that I've been planning to put in, but worst case is I have to put a new block in it.
 
#16 ·
Soooo you're not gonna just put the plugs back in and try and start it? I think you're wasting time and money. If your car wasn't running poorly before I don't believe you're gonna have an issue replacing the plug. A buddy of mine had the same issue with his supercharged srt8. Put a new plug in and went down the road. But It's what your wanna do. Just my opinion.


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#17 ·
Soooo you're not gonna just put the plugs back in and try and start it? I think you're wasting time and money. If your car wasn't running poorly before I don't believe you're gonna have an issue replacing the plug. A buddy of mine had the same issue with his supercharged srt8. Put a new plug in and went down the road. But It's what your wanna do. Just my opinion.

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I'm not going to risk any more damage. I'm also not close to the car right now to do the work myself. It was having a slight issue before I pulled the plug. I had a stutter/miss when I got into the powerband, so I'm going to play it a little safer than sorry on this one. Best case scenario, it passed with no damage. Replace the rest of the plugs and coil, and its on its way.
 
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