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2nd04Durango
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Discussion Starter #1
I recently ran into a situation that had me stumped. I have never had a vehicle that required exact and specific spark plugs. If it fit (threads, depth, gap and length of plug) and sparked then it should work just fine just like the other dozens of vehicles I have owned, driven or fixed. Yet for some reason my 04 Durango with 4.7L started running rough, stumbling and stalling after replacing the spark plugs.

The old ones had at least 0.1 to 0.2 worth of gap in there with the contact corroded/melted down, I suspect the dealership that sold this Durango to us 60K miles ago did not change them out as they claimed they did, meaning these plugs have anywhere from 90K to 120K miles on them (my D is almost right at 120K miles). Also the plugs were coated with rust, even though the coils have the rubber o-ring to keep moisture out. I have never seen spark plugs covered in rust like this unless they are at least 5 or 6 years old, especially on newer vehicles where they are sealed up under the coil most of the time. I have pulled spark plugs that were almost 10 years old that didn't have this much rust.

Picture of old plugs next to a new autolite.



Anyways, I finally found out what was causing the stumbling and rough idle... the plugs.

Everywhere I read was to use copper based plugs, so I did: Autolite 5224 copper plugs.

Apparently the resistance or something in these Dodge systems is so picky, it REQUIRES the specific resistance of the original Champion RC12MCC4 plugs (for 4.7L) which is somehow different from other plugs. I talked to the automotive repair (also a manager) friend I know and something about these 2000-newer engines require these plugs. They even have problems with the higher end platinum and premium based plugs which he said some scamming dealerships recommend to people to get them to come back and pay more for troubleshooting why it is idling and running rough making them more money. The only time when other plugs can be used safely is when the PCM is modified with something like Superchips that alters the timing that allows for premium/platinum plugs with slightly different (usually faster) spark rates.

I found ONE local auto parts store that had the specific plugs I needed (and not bad at $2 ea, versus $2.50 per 2 pack of the Autolites). As soon as all 8 were swapped out, the D ran better than it did with the old plugs that had 90-120K miles on them. Better power, and will most likely get better gas mileage.

Plugs required for the 4.7L engine from 2000+:

4.7L - RC12MCC4 (Champion)


Also found this online:

R = Resistor
C = 14MM thread with 3/4" reach
12 = heat range
M = Projected core Nose
CC = double copper
4 = wide gap required

 

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Busted Knuckle Garage
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531 Posts
Yeah I always stick to OEM spec plugs. Usually cheap enough and fewer headaches than trying to figure out an upgrade or use whatever you already have that isn't quite the same.
 

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2nd04Durango
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Discussion Starter #3
That was the strange part... this is the first vehicle I have ever run into where this was required. I hope this isn't a sign of things to come or I will start buying classic vehicles again and not worry about this proprietary computerized crap.
 

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Registered
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I think your rough idle came from moisture getting down past your coil and into the plug hole... Thats what caused the rust anyhow... and if they where that rusty then you definatley have unwanted moisture around your plug....

This is normally caused by a bad seal on your coil pack... If the the o-ring seal on the coil is bad, then water and moisture gets in and it runs like POO and forms rust over time. There is also a flap style seal on the coil packs that devert larger amounts of water ....

I have had experience with bad coil seals that have allowed water to enter and get around the plugs... they can make the truck feel down right broke down if water gets into them. Normally I know right away because it will be right after a heavy down pour or engine wash.

I dont beleive your problem was plug style... Im more convinced you have bad seals on your coils.

To date I have run just about every brand/style plug on my 4.7L since 2002 and have found the best all round performing plugs to be the NGK Iridiums... They last longer than any other plug I have used and you can feel the difference.

SPEED SAFE, NICK
 

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Registered
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4,261 Posts
To date I have run just about every brand/style plug on my 4.7L since 2002 and have found the best all round performing plugs to be the NGK Iridiums... They last longer than any other plug I have used and you can feel the difference.

SPEED SAFE, NICK
I agree my first set of NGK Iridium plugs are still going in the 06 4.7. Engine is now approaching 50K miles and they have been in there since 15K.
 

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All engines have a required thread size, reach, and heat range plug.
 
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