[RaggedOleMan]

My heep has 130k on it. The last time I changed out the spark plugs was at 50k. It was running fine, no red flags or issues, I just thought it wise to change them out before I had a problem. I’ve read many threads on various forums about which brand & model plug folks are using, but, there always seemed to be conflict. So, I just went to the Jeep dealer in town, paid their prices.

2005 Jeep Tj, 4.0/I-6, 6spd

Plugs; Mopar/NGK ZFR5N
Cost; $22.20 ($3.70 each…)
Tax; $ 2.06

The factory service manual (FSM) indicates the following;

Plug Gap; .030 to .035
Plug Torque; 22ft lbs

Socket sizes;
13mm coil rail
5/8" Spark plugs

The coil rail torque in the FSM was unclear to me. Best I could discern was 20 ft/lbs. Also, I put a light coat of anti seize on the threads of each plug, and the 4 coil rail bolts. Hope that wasn't a screw up...anyway...

I set out to change them. I started at the rear of the engine, closest to the fire wall, and for the purposes of this write up I’ll call that one #1. Here’s what I found;

The 1st plug gap had grown to .070



The 2nd plug gap had grown to .053



The 3td plug gap had grown to .058



The 4th plug gap had grown to .067



The 5th plug gap had grown to .070



The 6th (closest to the radiator/front) gap had grown to .055

The 6th plug appears to different from the others. Any thoughts as to what the conditions on the electrode(s) suggest?

Last, my heep overheated a few months ago while up at Naches/Manastash as a result of a blown, plastic cap on the flush/fill kit adapter kit (Prestone) that I installed a few years ago. It actually overheated 3 or 4 times total that day before I got it solved. My thought is the conditions of the majority of the plugs showed some indication of the overheating/preignition episode(s). But, I just guessing. What can you guys tell by looking at these photos?

[GOLENJEEPTJ]

They should have been replaced 50,000 miles ago!At least cleaned an re gapped!It's called preventative maintenance!No wonder you refer to it as a HEEP!

[CrzyMtnMan]

I would not be alarmed by it, basically the plug in question shows what you will normally find. The only thing that jumps out is perhaps fuel additive or high octane fuel. Reading a plug in any multiple cylinder engine over many miles will yield different results. I only recommend reading plugs if you are tuning a high performance engine and racing it.

[joeksjeep]

uhm as a mopar tech and life long mopar lover, they seem to hate anything that doesnt say champion.. Im extremely suprised to hear the delaer gave you ngk. I always use champion, when i dont i get problems, and always have

[chris142]

I wonder what kind of effect these old worn out plugs have on coil life and Cat converter life?

[RaggedOleMan]

Originally Posted by joeksjeep

uhm as a mopar tech and life long mopar lover, they seem to hate anything that doesnt say champion.. Im extremely suprised to hear the delaer gave you ngk. I always use champion, when i dont i get problems, and always have

Interesting...the last set I bought and installed also came from a Jeep dealer, however, that dealer was in Seattle, WA. They sold me the NGK's, as did the dealer in Tacoma, WA just today.

I've heard/read positive comments about "Champion", too. But I assure you, my heep idles and runs flawlessly since the day I bought it new in April of 2005. And on NGK's ZFR5N's.

In fact, the Mopar box they came in says right on it; 6-SP000ZFR5N

[joeksjeep]

o ya i know it will idle fine and will run better than it did with old plugs, but from my experience if you put it on an ignition scope you will see glitches that you dont see with champions.. Its very minut, and i dont know the long term affects because i have always switched em out with champions... These are for the true mopar motors, liek the 4.0, 5.9 nd such, not the mitsu 4 and 6 cyl idk

[TJJP77]

You really shouldn't run plugs that long in a 4.0L - it uses a "waste spark" system that fires the plugs on the exhaust stroke as well. Mine were up to around .050 with only 28K on them!

And for the record, Jeep did switch from the Champions to the NGK plugs as OEM install somewhere towards the end of the 4.0L's life...I can't imagine it was for cost reasons as the NGKs are probably pricier plugs than the Champions...they must have had a good reason.

[Border Dave]

Originally Posted by joeksjeep

... These are for the true mopar motors, liek the 4.0, 5.9 nd such, not the mitsu 4 and 6 cyl idk

If you're referring to our inline 6 cylinder 4.0, it is not a Mopar motor; it's an AMC motor. The 5.2 and 5.9 Magnum engines were derived from the AMC 318 and 360, repectively.

[CrzyMtnMan]

Originally Posted by TJJP77

...And for the record, Jeep did switch from the Champions to the NGK plugs as OEM install somewhere towards the end of the 4.0L's life...I can't imagine it was for cost reasons as the NGKs are probably pricier plugs than the Champions...they must have had a good reason.

This seems to ring a bell, wasn't there some issue too with the platinum plugs around that time as well, I seem to remember some plug related come-backs in the dealership, I can not put my finger on it, but this does ring a bell there was a big reason for the change.

I will fess up a mistake, never use Bosch, , I have never had a spark plug fail, about 4 months after putting them into the Neon I had one of those fail, and a year later was starting to have the same power loss issue. In fact I was getting ready to change them just before it was totalled. If anyone has a need for 4 NGK BKR6E spark plugs, I will gladly send them to you for free, forgot I hung on to them.

[Recoil]

Just picked up 6 Champion 7034s today to throw in my rig

[SnoqulmieTJ]

Ragged that is just normal wear and tear, as for the should have changed them 50k miles ago no wonder you refer to it as your heap commment from Golenjeeptj, why say something like that? I know you have alot of stoc in pepboys, and if not then you must be their best costomer. plugs can go well past the recomended milage if you take care of your "Heap" I.E. oil changes, use good fuel, and if you drive alot on the highway then they will last a long time. Now for regapping them, and cleaning them that is just common knowledge. I dont know why people hop on these forums and say stuipid stuff towards another Jeep person.

[robncar]

Originally Posted by SnoqulmieTJ

...as for the should have changed them 50k miles ago no wonder you refer to it as your heap commment from Golenjeeptj, why say something like that?...

...I dont know why people hop on these forums and say stuipid stuff towards another Jeep person.

Perhaps it was a joke? You know, humor...

Did you notice the at the end of the post?

[RaggedOleMan]

Originally Posted by SnoqulmieTJ

Ragged that is just normal wear and tear, as for the should have changed them 50k miles ago no wonder you refer to it as your heap commment from Golenjeeptj, why say something like that? I know you have alot of stoc in pepboys, and if not then you must be their best costomer. plugs can go well past the recomended milage if you take care of your "Heap" I.E. oil changes, use good fuel, and if you drive alot on the highway then they will last a long time. Now for regapping them, and cleaning them that is just common knowledge. I dont know why people hop on these forums and say stuipid stuff towards another Jeep person.

Regarding my reference to my own heep, as a "heep", it's just sillyness on my part. And while my maintenance schedule & practices could be improved, my 2005, Jeep Tj w/inline 6 has been the most reliable vehicle I've ever purchased, bar none. It has never left me stranded on the pavement or on a trail...and it sees a lot of trail duty. When I call my heep a heep, I say it with great affection...

Let's give Golenjeeptj the benefit of the doubt!

[Mindcrime13]

i went to autozone and got champion 438 are they ok for my 2006 I6?, the guy told me that i should use bosch, the only reaon he said is that because they cost about 1 dollar more than the champios....