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Discussion Starter #1
I did some limited research online to change the plugs on the wifes commander. Seemed cut and dry. Upon arrival to the auto parts store, they stated i needed 4 iridium and 4 copper plugs. Don't recall which was for intake and which for exhaust. Anybody else come across this? I will be taking out the existing plugs to see whats on the truck. Any info or experience would be appreciated.
 

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Too bad you don't have a Hemi - they use 16 spark plugs:) I'd stay away from that auto parts store.
 

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What do you need plugs for exhaust?? I did 8 of the same in my 4.7. Watch they may next recommend you replace the muffler bearings
 

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What do you need plugs for exhaust?? I did 8 of the same in my 4.7. Watch they may next recommend you replace the muffler bearings
Or headlight fluid.
 

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That would only be *8 plugs in total, but two different kinds of plugs, Sounds like a scam Or they think you have a Hemi v4 :gotrice:
 

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Discussion Starter #8
It does have the "waste spark" for the exhaust, which is an iridium plug that the manual stated need replacement at 100k. I changed the 8 copper intake plugs located underneath the coils. Hope this helps in the future. There was limited info about the engine on this site. :alfdance:
 

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Discussion Starter #9
Also, it does take 16 plugs (8 iridium/8 copper). Not 4 and 4 as i was first led to believe.
 

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Why is everyone talking about intake and exhaust spark plugs? Spark plugs fire either on the compression stroke or power stroke. Spark on intake would cause a backfire through the intake and on Exhaust probably something in the tail pipe. Or is this 4.7 engine also converted to 2 cycle?
 

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Its semantics for a generic discussion. Everyone knows the terms intake and exhaust but not everyone knows the names of the strokes. Obviously they dont fire when valves are open. Exhaust "cycle" is more correct than exhaust "stroke" but the points the same for those who arent analyzing each specific stroke per cycle
 

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It would be Power Stroke and Exhaust Stroke, or Power and Exhaust, maybe main and wasted spark. Actually the exhaust plug would fire when the valves were open or at least near being closed, but I'm nit-picking, what Matt is saying is accurate.

What I didn't hear in the thread, what does the '08 4.7L have OEM for plugs? With all the complaints about ignition problems after switching plug brands or types, the conventional wisdom has been to just replace the plugs with the exact same that it came with OEM.

There is a difference between single and double platinum/irridium, and the wasted spark system has reverse current on half its plugs, so if you apply reverse current on a single platinum/irridium plug it will errode much faster than a regular plug. Of course, they may have designed the motor so the Copper Champions have the reverse current and the single irridium is normal. Regardless, like is the conventional wisdom, just replace the plugs with the exact OEM part numbers and you should be fine.

I "suspect", but I don't really know, some larger engines, bigger bore cylinders have trouble getting complete burning of the fuel, and this hurts emmissions big time. So the 2nd plug may be there purely to meet emmissions, a 2nd spark at the end of the cycle to burn any left over fuel.
 
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