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Old 04-20-2013, 04:30 PM   #1
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Surprised by Spark plugs

I have a 2004 Wrangler Sport it has 115k on her at 113k I changed the original spark plugs with New Champion RC12ECC I gaped them to .035 I noticed an immediate drop in power and BIG fuel economy drop I went from getting 19MPG daily driving to work to 14-15MPG.

After about 2000 mi of this I decided last night to change the plugs back to the stock NGK Vpower ZFR5N well the difference is AMAZING I went skiing this morning and on the trip up the mountain I had much more power when cruising on the highway in 5th gear The trip was 175 mile round trip and I did it on a half a tank through the mountains !

I never knew spark plugs could cause so much difference in both power and MPG.

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Old 04-20-2013, 04:38 PM   #2
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Properly installed, there should have been no noticeable performance difference between those two plugs.

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Old 04-20-2013, 04:44 PM   #3
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Yea properly installed a week after installing the Champions I took the coil rail off again and pulled the plugs to recheck the Gap thinking when installing them I messed up the gap on one but all where correct .035 I had better power with the ones that had 113K on them and a .060 gap then the champions.

I was just shocked perhaps they where defective or something but I think I will stick with the NGK from now on.
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Old 04-20-2013, 04:45 PM   #4
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I gaped them to .035
Is that what the 2004 FSM calls for? I don't have a 2004 manual, but the 2003 FSM specifies .040" for the plug gap.
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Old 04-20-2013, 04:46 PM   #5
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Yup operator error on the first install would be my guess...probably something simple. But you can't go wrong with NGK's over champs...NGK makes a good plug.
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Old 04-20-2013, 04:49 PM   #6
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Yup operator error on the first install would be my guess...probably something simple.
"Operator error" typically reveals itself very quickly in the form of a badly running engine.
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Old 04-20-2013, 04:49 PM   #7
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Is that what the 2004 FSM calls for? I don't have a 2004 manual, but the 2003 FSM specifies .040 for the plug gap.
Thats whats on the sticker under the hood shows that NGK Vpower ZFR5N plug and an.035 gap.
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Old 04-20-2013, 04:52 PM   #8
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Yup operator error on the first install would be my guess...probably something simple. But you can't go wrong with NGK's over champs...NGK makes a good plug.
No operator error been working on cars since I was a kid about 20 years. that's why I pulled the plugs again to make sure I did not bump the tip of the plug but I found nothing wrong with them even made sure the rail was fully on. Jeep ran smooth and idled fine just did not have the power.
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Old 04-20-2013, 04:56 PM   #9
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Length of time working on cars doesn't mean an occasional error can't be made. I turned my first automotive wrench back in probably '64 & I still find the occasional screw-up from a brain fart.
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Old 04-20-2013, 04:57 PM   #10
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Is that what the 2004 FSM calls for? I don't have a 2004 manual, but the 2003 FSM specifies .040" for the plug gap.
It sure does call for a .040 Gap in the 03 FSM I just double checked my Emissions Tag under the hood and it says .035 strange
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Old 04-20-2013, 05:03 PM   #11
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Length of time working on cars doesn't mean an occasional error can't be made. I turned my first automotive wrench back in probably '64 & I still find the occasional screw-up from a brain fart.
There's not much to screw up on spark plugs especially to have such a dramatic change in performance and I did go back and checked each plug over again. I am going with the reason as defective plugs as this is the first time I've ever had this happen on any of the cars I've ever had.
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Old 04-20-2013, 05:09 PM   #12
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I had the same issue with my 04 Rubicon. I was trying to save some money and went with the cheaper model champion I could feel the difference right off the bat. Loss of power and MPG loss too. I would have to press harder on the gas to get her up to highway speed and my passing power was gone my MPG was at 12 down from 16. Changed the plugs with stock NGK and WHAM all power back and was getting 17 MPG....Wierd.
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Old 04-20-2013, 09:44 PM   #13
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Mega weird
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Old 04-20-2013, 10:33 PM   #14
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I deal with three brands of plugs on a daily basis at work, champion, autolite, and bosch.In the last 6 months almost every set of champions I have installed has had at least 1 bad plug in the box. Not sure what happened at champion recently but I think they have some QC issues.
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Old 04-21-2013, 06:44 PM   #15
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Well just filled up and I got 325 miles for the tank filled up with 16 gallons for 20.3 MPG up from 14 MPG with the champion plugs. I think it must have been a bad plug I can't believe that major difference just changing brands.
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Old 04-21-2013, 06:50 PM   #16
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Well just filled up and I got 325 miles for the tank filled up with 16 gallons for 20.3 MPG up from 14 MPG with the champion plugs. I think it must have been a bad plug I can't believe that major difference just changing brands.
Would that be a 4 banger.??
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Old 04-21-2013, 06:55 PM   #17
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I just want to know how in the world you get 20 mpg in a TJ. Me and my daughter must be doing something really wrong. Congrats on that.
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Old 04-21-2013, 06:59 PM   #18
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I just want to know how in the world you get 20 mpg in a TJ. Me and my daughter must be doing something really wrong. Congrats on that.
I got that on the highway when it was stock...driving like a Grandpa..but we all know once you start Modding that is all out the window!!
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Old 04-21-2013, 07:23 PM   #19
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I just want to know how in the world you get 20 mpg in a TJ. Me and my daughter must be doing something really wrong. Congrats on that.
I get that alot I live in Denver and use 85 octane gas. I have 33"X10.5 BFG/AT and 4.10 gears. I drive back and forth to work on the highway @ 65 MPH and get between 18.5 and 20 MPG all the time. I use cruise a lot Shift early I never go over 2k RPM when accelerating and am in 5th gear before 40 MPH. I do have a Banks CAI and Throttle body spacer.

I hear many people with the 4.0L call me a liar and say it is impossible to get 20 MPG but I do it all the time. I've checked the tripometer and speedometer and both are very accurate. My friend a cop has Lasered me at 60 MPH on cruise and was dead on.

I run Synthetic in everything I don't hit the gas hard I try keeping it in 5th gear as much as possible and don't exceed 65 on the highway. I don't have a lot of Weight on the jeep Warn Stubby bumper and warn zeon winch are the heaviest thing on it.

Perhaps try a different set of plugs the NGK seem to work real well.
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Old 04-24-2013, 10:35 PM   #20
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What part number are these magic NGKs?
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Old 04-24-2013, 10:42 PM   #21
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I deal with three brands of plugs on a daily basis at work, champion, autolite, and bosch.In the last 6 months almost every set of champions I have installed has had at least 1 bad plug in the box. Not sure what happened at champion recently but I think they have some QC issues.
Yeah their made in Mexico now crap
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Old 04-24-2013, 10:47 PM   #22
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I call BS, a sparkplug lights the combustion process and thats all if it's not doing that you have a noticeable misfire or fishbite. No sparkplug no matter the quality, cost or advertising will make the differance in MPG your saying.
There's something your missing or your miscalculating mileage.
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Old 04-24-2013, 11:30 PM   #23
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What part number are these magic NGKs?
ZFR5N

Made in Japan.

Not to be confused with poor quality "imported" plugs, as they are not, they just work. I don't care about them lasting 100k because I'm going to check them out every 30k anyway.
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Old 04-24-2013, 11:49 PM   #24
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How can one tell if you have a "bad" plug or if one of them is not gapped right (A side from visual inspection). When I had my jeep tuned up at my garage, I tried to find NGK's but Canadian tire was sold out so I went with Champions as next best option to be installed. Having no prior experience with jeeps leaves me with limited knowledge. They were put in last summer, and based on what I read so far on this thread I'm not sure if my mechanic had gapped them right or even did(human error).

Would I be wasting my time to pull them all out and check it myself and/or get NGK's instead?
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Old 04-25-2013, 12:14 AM   #25
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ZFR5N

Made in Japan.

Not to be confused with poor quality "imported" plugs, as they are not, they just work. I don't care about them lasting 100k because I'm going to check them out every 30k anyway.
Cool. Thanks. I run NGK in my r1 so I'm no stranger to them... I recently replaced mine with champions (or was it autolites?) but my gas mileage is nothing compared to others in that MPG thread. So as simple and cheap as it is to swap these, I think I'll give them a try. If I recall correctly, that was the same part number of the ones I removed. I, also, am not too worried about plugs lasting a lifetime.
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Old 04-25-2013, 01:07 AM   #26
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How can one tell if you have a "bad" plug or if one of them is not gapped right (A side from visual inspection). When I had my jeep tuned up at my garage, I tried to find NGK's but Canadian tire was sold out so I went with Champions as next best option to be installed. Having no prior experience with jeeps leaves me with limited knowledge. They were put in last summer, and based on what I read so far on this thread I'm not sure if my mechanic had gapped them right or even did(human error).

Would I be wasting my time to pull them all out and check it myself and/or get NGK's instead?
You can pick up a plug gap gauge at most auto stores
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Old 04-25-2013, 07:23 AM   #27
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Are the NGKs already gapped correctly?
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Old 04-25-2013, 07:52 AM   #28
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I do have a Banks CAI and Throttle body spacer.
Gotta be the spacer. Moving the butterfly valve upstream on a downstream fuel injected vehicle really wakes it up...
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Old 04-25-2013, 12:17 PM   #29
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Are the NGKs already gapped correctly?
not only are they gapped correctly but they have a cardboard sleeve to protect the electrode/threads during shipping.

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Old 04-25-2013, 12:25 PM   #30
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Gotta be the spacer. Moving the butterfly valve upstream on a downstream fuel injected vehicle really wakes it up...

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