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Old 12-20-2012, 05:31 PM   #1
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New Plugs 03 4.0

After only having my new jeep for about a month, I decided to change the plugs. The jeep showed no signs of misfire or hesitation, but for my piece of mind and not knowing how old the plugs were, I decided to change them anyway.. Plus, with 86,000 I was kinda curious what type of plugs they were running. Bosch Platlium +4 were in it and they looked a little wore out.. I installed the NGK V-Power and it seems to start faster and Idels around 750 in park. (Auto).. The big thing I notice was that a vibration in the dash I had when I would first take off for a second or two is gone. Seemed kinda weird, but I should know a little more by the weekend.. Also, the Coil pack setup was a little new and was hoping I got all the boots seated correctly.. If I did have one not all the way on, what type of signs would show.. I dont have any missing or notice anything really different between the two plugs, besides the quicker start and vibration gone..
Here is a pick of the Bosch plugs.. Not sure how many miles are on these..

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Old 12-20-2012, 06:56 PM   #2
Knows a couple things...

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Bosch Plus2 & Plus4 plugs are a terrible choice of spark plug for our Jeep engines... and in general, Bosch plugs just don't run well in Jeep engines... something to do with their heat range not being a good match.

Three known-good spark plugs that always perform well in 2000 and newer engines which have the DIS (distributorless ignition system) ignition include the Autolite XP-985, Autolite APP-985, or Champion 7034. 2000 and newer engines are, due to the DIS ignition, especially fussy about the spark plugs they like to run well on.

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Old 12-20-2012, 07:21 PM   #3
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Jerry what do you know about those NGK ZFR5N I just put in? I will give them a few weeks and switch them out to those you recommend if my milage and performance decrease.. Thanks again for your insight, not just on this topic, but all the others you help us noobs out..

OH, I was thinking about the vibration and I wonder if maybe the Tranny Dipstick was close to firewall. Seems like I have read something like that, maybe I shifted it a little when removing the coil pack...
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Old 12-20-2012, 07:42 PM   #4
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NGK ZFR5N spark plugs were original equipment for an '03 model. They work fine; keep them for at least the next 25k miles.
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Old 12-20-2012, 07:52 PM   #5
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Quote:
Originally Posted by tangofox007 View Post
NGK ZFR5N spark plugs were original equipment for an '03 model. They work fine; keep them for at least the next 25k miles.
Good to know I at least have it back to factory specs..
Thanks
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Old 12-20-2012, 08:21 PM   #6
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What a coincidence

I joined the site today in large part to see if I can get some advice as to working on my '06 Golden Eagle. I've never really worked on my vechicles in the past but just bought this over last summer and would like to try. I've had disappointing MPG and think plugs may be the culprit. I have a straight six cylinder and it looks easy enough to change them out myself. I'll need to get some tools but is it as easy as it appears? Thanks!
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Old 12-20-2012, 08:33 PM   #7
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What did you gap the plugs to?
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Old 12-20-2012, 09:31 PM   #8
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Gap was set at .035

Here is a link below that is helpful.. Pretty easy stuff

Jeep Spark Plug Remove and Install
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Old 12-20-2012, 09:50 PM   #9
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Quote:
Originally Posted by Rooster21 View Post
Gap was set at .035

Here is a link below that is helpful.. Pretty easy stuff

Jeep Spark Plug Remove and Install
I would recommend that you consult the service manual for your year model instead of relying on internet articles. Had you done that, you would have found that the recommended spark plug gap for an '03 model is 0.040" and the recommended torque is only 22 ft/lbs. And you would have seen the caution against overtightening the plugs, which is exactly wht you did if you followed the advice in your link.
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Old 12-21-2012, 11:10 AM   #10
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Does anyone have an estimated time on how long this should take a newbie to car maintenance? I am building a list of what to tackle to my recent purchase and this is up there. 1 weekend at a time.
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Old 12-21-2012, 11:36 AM   #11
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Did this last weekend on a friends Jeep and it took longer to get the plugs than remove and install them. 30 minutes.

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