Double platinum spark plugs made me lose power. WHY? - JeepForum.com
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post #1 of 48 Old 08-22-2021, 08:16 AM Thread Starter
Cobra Jeep
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Double platinum spark plugs made me lose power. WHY?

99 WJ 4.0
I rebuilt the engine a couple years ago. A few weeks ago I was changing the oil in it and I was curious how many miles I had on the new engine. I looked at my records and I have 21,000 miles on it. The spark plugs that were in it, I put in when I built the engine. Champion RC12ECC.
I know it was a little sooner than the recommended 30K, but I like staying on top of maintenance. So I decided to go ahead and change them. It is not going to hurt anything.
I got looking around online and see people recommending double platinum spark plugs for the waste spark ignition these engines have. So I drink the koolaid and buy a set of champion double platinum plugs (champion 7034).
I put them in on my lunch break one day and everything seems ok when driving it back to the parking lot. The old plugs had a little rounding of the electrodes, but nothing bad. They still looked pretty good, I have seen way worse.
I go home that afternoon and it seems like it is not accelerating like it used to. It feels like I have the cargo area chock full of several hundred pounds of equipment. Continuing to drive home, I notice it is slowing down on hills it never used to, and a couple of them, it had to downshift to get up. It had never downshifted on these hills before.
I starting thinking what the heck? All I did was change the spark plugs. I think maybe the computer just needs to readjust. So I continue to drive it for a couple more weeks like this with no change, being annoyed at the loss of power.
It starts normally, runs smoothly, no missfires, just it lost power.
I finally give up and buy a new set of the RC12ECC like I had in it. I swap them out on lunch last week. I drive home and it is instantly back to normal. No more slowing down on hills, it no longer downshifted on those hills and every was just like it was before the platinum plugs. No more power loss, it's back to running like it always has.

So I am dumbfounded as to WHY double platinum spark plugs made me lose a good bit of power? Can anyone give me any reason as the why this happened? The platinum plugs looked normal, the gaps were even and nothing had any visible damage or anything abnormal.


'93 YJ 4.6L stroker, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, home made front hub conversion, hydroboost. Warn M10000 winch.

'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.
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post #2 of 48 Old 08-22-2021, 09:05 AM
Mattyjm
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Jeep put out a Technical Service Bulletin that strongly recommended NOT using any plugs other than copper core in their 4.0L i6 and the 4.7L V8. The engines were built to a certain performance level with those spark plugs.

I've had three different misfire situations in three different WJs with the 4.0L i6 be corrected when I took out the P.O.'s iridium or platinum plugs and replaced them with NGK copper cores.

I can't explain it because I'm not an engineer, but there's not enough written or said about just sticking with OEM.

2004 Special Edition WJ. LOADED!
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post #3 of 48 Old 08-22-2021, 09:06 AM
rfesu
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it shouldn't make a difference. it's possible you got a defective plug (it happens)

personally i run NGK in everything, and i think old engines just tend to be fine with normal copper plugs...especially on an engine where it's so easy to change plugs, getting a longer service interval out of your plugs isn't really necessary
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post #4 of 48 Old 08-22-2021, 09:59 AM
retrvrtrainer
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I had the same experience with platinum plugs in mine. It does seem to run better with copper.
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post #5 of 48 Old 08-22-2021, 10:26 AM
mdwildcat04
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https://en.wikipedia.org/wiki/Wasted_spark_system

rare metal plugs hate waste spark ignitions.
Look at your coil pack, there are only 3 humps, it only has 3 coils, not 6.
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post #6 of 48 Old 08-22-2021, 12:24 PM
2oldjeeps
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if it aint broke???
i have some jeeps. high mileage ? 130000 to 180000.
been a jeep guy for just 5 yrs ?. i feel the 4/0 is powerful for a 6.
i have never seen a jeep plug. may never.
if it aint broke....

99wj, 150,000 miles
00xj ,189,000 miles
10hummer3,76,000 miles
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post #7 of 48 Old 08-22-2021, 05:04 PM Thread Starter
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Quote:
Originally Posted by Mattyjm View Post
Jeep put out a Technical Service Bulletin that strongly recommended NOT using any plugs other than copper core in their 4.0L i6 and the 4.7L V8. The engines were built to a certain performance level with those spark plugs.

I've had three different misfire situations in three different WJs with the 4.0L i6 be corrected when I took out the P.O.'s iridium or platinum plugs and replaced them with NGK copper cores.

I can't explain it because I'm not an engineer, but there's not enough written or said about just sticking with OEM.
Yep, and that is why I went back with the RC12ECC. The sticker under the hood of my WJ specifically says those plugs, so that is what I have been using up until the platinum ones. I will be using the RC12ECC from now on.

'93 YJ 4.6L stroker, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, home made front hub conversion, hydroboost. Warn M10000 winch.

'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.
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post #8 of 48 Old 08-22-2021, 05:07 PM Thread Starter
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Quote:
Originally Posted by mdwildcat04 View Post
https://en.wikipedia.org/wiki/Wasted_spark_system

rare metal plugs hate waste spark ignitions.
Funny you say that, the link you posted specifically say to use precious metal spark plugs (platinum/iridium). As well as most of the places I saw online.
Oh well, I will never use anything other than a copper spark plug in any of my engines.
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'93 YJ 4.6L stroker, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, home made front hub conversion, hydroboost. Warn M10000 winch.

'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.
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post #9 of 48 Old 08-23-2021, 12:56 AM
jw11432
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Copper plugs have less resistance, so you get a more powerful spark. This translates to a more complete burn, but also wears the plug faster. Precious metal plugs are higher resistance, but also last longer. They were really designed for people who like to do less maintenance on their vehicles.
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post #10 of 48 Old 08-23-2021, 09:46 AM
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I used to design spark plugs for turbine engines back at Unison in FL twenty years ago. I am a materials engineer (MS) though specializing in ceramics.

Pt electrodes should be used when erosion is the main concern. Sparks liberate a tiny bit of metal with each event. Pt resists erosion better than standard plugs. That’s why plugs round off over time. Spark ya like to jump from sharp corners & these erode over time. Iridium does much the same thing. If you have trouble getting to / reaching plugs to change then yes by all means use them. If access isn’t a problem there’s only the downside of slightly greater resistance and slightly less energy with each spark event.

Double ground electrodes is a marketing ploy also really. It does allow the center electrode to use more of its sharp edges BUT it also shields the gas from the spark also. Gimmic really.
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post #11 of 48 Old 08-24-2021, 08:21 AM
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Quote:
Originally Posted by Cobra Jeep View Post
Funny you say that, the link you posted specifically say to use precious metal spark plugs (platinum/iridium). As well as most of the places I saw online.
Oh well, I will never use anything other than a copper spark plug in any of my engines.
Ya, I need to learn to read.......

When I had a Saturn SL2, I was a member of a saturn forum. It was like clockwork, a new member would join and complain of poor performance and mileage after a tune-up. It was always platinum plugs.... The Saturn 1.9 HATES platinum plugs. some would try to argue because they drank the kool-aid, but every one that switched to NGK coppers, saw a vast improvement.

I guess the real rule of thumb, on ignition systems, use what it was designed for........
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post #12 of 48 Old 08-27-2021, 01:05 PM
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The Champion OE plugs are CHEAP too. I think they were like $7 from Rock Auto.

1999 WJ Limted - Ex Soccer Mom ride turned Rule 25 Compliant Bike Hauler
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post #13 of 48 Old 08-27-2021, 02:51 PM
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The advice that I received from a person much more knowledgable that myself on the subject went along the lines of: "These motors(4.0L i6) were designed to use that spark plug and won't really benefit from any change to that spec". Use the factory recommended plug. Don't waste your time or money on stuff that won't get you anything. The 4.0 is not a performance motor. It was never meant to be one.
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post #14 of 48 Old 08-27-2021, 03:11 PM
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Quote:
Originally Posted by RavenWJ View Post
The advice that I received from a person much more knowledgable that myself on the subject went along the lines of: "These motors(4.0L i6) were designed to use that spark plug and won't really benefit from any change to that spec". Use the factory recommended plug. Don't waste your time or money on stuff that won't get you anything. The 4.0 is not a performance motor. It was never meant to be one.
My 4.0 is a super performance engine compared to my first 2.5!
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post #15 of 48 Old 08-28-2021, 06:32 PM
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Quote:
Originally Posted by Mattyjm View Post
Jeep put out a Technical Service Bulletin that strongly recommended NOT using any plugs other than copper core in their 4.0L i6 and the 4.7L V8. The engines were built to a certain performance level with those spark plugs.

I've had three different misfire situations in three different WJs with the 4.0L i6 be corrected when I took out the P.O.'s iridium or platinum plugs and replaced them with NGK copper cores.

I can't explain it because I'm not an engineer, but there's not enough written or said about just sticking with OEM.
Read and heed.... +1
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