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Unread 10-28-2014, 09:35 AM   #1
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Join Date: Aug 2014
Location: Boston, Ma
Posts: 10
2004 4.0 sparkplugs # needed

I have to change the valve cover on my daughters car and will also like to change the plugs at the same time.

Its a 2004 grand Cherokee with the 4.0 6 cylinder.

pep boys shoe a champion #438 for the plug. I would like to stay with the OEM plug.

Getting the parts at Pep Boys where my other daughter works get 20% discount not much but it helps.

I did not pull the plugs yet as this will be done in the morning and she is using the car at the moment for the day.

I have the gasket just need a correct plug # OEM for this 2004 4.0 engine.


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Unread 10-28-2014, 01:22 PM   #2
1997 ZJ 
Join Date: Apr 2009
Location: mass
Posts: 4,830
Not sure of the number, but I run Champions in my 4.0 2004 Grand Cherokee and they are fine.

Call our sales staff 866-403-3393
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Unread 10-29-2014, 10:22 AM   #3
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Location: Boston, Ma
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I JUST GOT THROUGH BOUT 1 HOUR AGO CHANGING THE VALVE COVER GASKET and the spark plugs, for both about 3hrs or less.

The plugs were completely bad most of the electrodes were worn away. They were champion RC12PEC5 in there. I put in the champion 438 RC12ECC and the car purrs like it should.
Bought the car with 132k and now 173k never change the plugs when I bought the car for my daughter. I have to see what the RC12PEC5 plug is to the RE12ECC that belongs in there.
No sign of oil just the normal brown color on plugs.
Had to change the valve cover gasket it was leaking and I thought it was the rear main seal. You could tell the gasket was leaking in the rear as the oil was all over the top rear of engine and was leaking down, I hope time will tell. My other daughter works for Pep Boys so I got 20% off plugs and gasket. Gasket was kinda pricey $33.99 all the auto stores had that price. It was a felpro for the 4.0 6 cylinder.

Well when I change plugs on my vehicles for the past 45 yrs I always used the ones the engine calls for and never have i had a problem.
I will report back here when daughter takes the jeep out for a ride and see if all is aok. She is using my 2005 Dodge Durango Limited and should be home later.

One thing is I don't know how the engine could of run the way it did with the worn plugs here is a picture of one.
Just looked up the plug they are platinum I wish I knew how long they were in there to compare to the wearing away of the platinum electrode.

Platinum conductor; Center electrode platinum tip wears less than a standard spark plug; This allows the plug to maintain the gap setting throughout its life
Exclusive heat-active alloy allows the electrodes to reach optimal temperature quickly and maintain stable operating temperature under all engine loads
Platinum center electrode
V-trimmed electrode
Replacements for standard spark plugs and OE coil-on-plugs
Increased efficiency and reliability

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