[Jeepahaulic]

I’ve had my TJ less than a year and I have not changed the plugs yet. It has always ran perfectly save for an occasional miss at cold starts. At idle, for maybe 2seconds. Once I bump the throttle, it purrs like a tiger.
It never fires on the first try..I let it crank maybe 5 seconds. Second try it fires immediately. I’m feeling pretty sure this is simply the fuel pressure building.

Anywho…what brand do you guys prefer?

 

[Burnit53]

I only use NGK plugs. Chevy, Jeep, Honda, etc..

 

[Jerry Bransford]

There are a lot of good spark plugs but I have settled on the Autolite XP-985 which has an iridium-coated electrode and "fine wire" technology which helps it provide a solid spark in even difficult combustion situations. Iridium and fine wire technology is not just available from Autolite, it's a proven technology that other brands provide too. But I sure like my XP-995 plugs I've run in two TJs over the past 18-20 years. Not to mention lab tests have shown the life of this plug to be over 200k miles.

One more point... if your TJ is new enough to have the coil rail ignition system (no distributor or spark plug wires), it is fussy about platinum plugs if you want to run platinum which is another good choice, just not as long lasting as iridium is. Newer coil rail TJs will not run properly (they will miss and have a bad idle) with "single-tipped" platinum but they will run fine with "double-tipped" platinum. Single-tipped means the platinum is on just one side of the gap, double-tipped means the platinum coating is on both sides of the spark gap. Platinum plugs are good for about 100k miles.

 

[Burnit53]

Another point about Platinum tipped plugs... When I was wreching for Honda no non-oe part gave customers more issues than Bosch Platinum plugs. Misfires. Guaranteed. Every time!

 

[Jerry Bransford]

Another point about Platinum tipped plugs... When I was wreching for Honda no non-oe part gave customers more issues than Bosch Platinum plugs. Misfires. Guaranteed. Every time!

Were they single or double-tipped? Were your Honda ignition systems waste-spark designs?

 

[Burnit53]

Whatever the typical Bosch Plats are. They are junk. A google search will net you pages of problems with these plugs in nearly all manufacturers.

Hondas are not waste spark.

 

[Mattaeus]

if your TJ is new enough to have the coil rail ignition system (no distributor or spark plug wires), it is fussy about platinum plugs

Platinum plugs are good for about 100k miles.

That's because the heat range of platinum and iridium plugs are out of spec for the Jeep engine. The Jeep engine is 8.8:1 compression. It needs a hot plug. Platinum and iridium plugs are only available for the manufacturers to make more money. They feature the same damn copper/nickel core as every other plug, just a silly coating. It's snake oil. If it wasn't snake oil, every single racing team, with money on the line, would be using them. You know what every single racing team uses for plugs? Copper/nickel, because it's the most conductive and most repeatable.

The brand shouldn't matter too much. What matters is the material, heat range and reach. For the Jeep engine, you need a copper/nickel plug, heat range 5, with .75" of reach. 14 MM threads, 5/8" hex and .026"-.036" Gap. ZFR5N are the optimal plugs for the stock setup, BCPR6E for under 10 PSI, ZFR7F for over 10 PSI (manifold pressure).

 

[Burnit53]

Not 100% true.

Most auto manufacturers install platinum plugs new. They offer extended life over the basic counterparts. Most went from spark plug change at 30k to over 100k when they went platinum.

 

[Mattaeus]

Most went from spark plug change at 30k to over 100k when they went platinum.

You drank the damn snake oil didn't you. It's just a protective coating brother. It bumps up the heat range and drops the conductivity/performance. They're good for old women who can't turn a wrench.

 

[Burnit53]

You drank the damn snake oil didn't you. It's just a protective coating brother. It bumps up the heat range and drops the conductivity/performance. They're good for old women who can't turn a wrench.

It's not snake oil.

I've probably changed a couple thousand plugs in my automotive career. The wear on a standard tip plug is very noticeable over 30k. Enough to get drivability issues. Doesn't happen with Platinum and Iridium plugs. Do you think an auto manufacture would waste money on 100s of thousands of engines every year because "snake oil"? No, they did it to extend service intervals.

 

[Jerry Bransford]

Curiosity got the best of me and made me realize why I had blocked Mattaeus and his baseless inflammatory bull$hit posts years ago, Back on block.

 

[Burnit53]

I'm not recommending he do anything. Just stating facts about spark plug tech. You really should brush up on a subject before you start telling the internet how to do it.

A 5 heat range plug by one manufacturer isn't necessarily a 5 for another. NGK 5 is a Bosch 8, and Champion 11/12.

And, I can get a Platinum NGK as low as 4. I run a 6 in my bored/stroked/big cam LS2...

Hopefully the OP got something useful out of all that.

 

[Mattaeus]

Just run the OE spec plugs

 

[Jeepahaulic]

Champion shows a 12 heat rating..
Autolite is 25…5 seems low in comparison?

 

[Burnit53]

They don't all use the same numbers, or even ascending/descending metric.


Random google image..

 

[Jerry Bransford]

They don't all use the same numbers, or even ascending/descending metric.


Random google image..
View attachment 4557835

That's a great chart, I have always wondered why there is no industry-wide standard for heat range numbers.

 

[KennethS]

Do you think an auto manufacture would waste money on 100s of thousands of engines every year because "snake oil"? No, they did it to extend service intervals.

Yes, and the reason for that extended interval is the federal emissions regulations that say the engine has to stay within emissions standards up to 100,00 miles. And we all know the majority of the public doesn't do any maintenance, so the manufacturers were burdened with developing a solution to the typical "no maintenance" owner. So if a person does regular maintenance, including spark plug changes, then regular nickel / copper spark plugs will work fine.

 

[Dustdevil]

Not a plug expert by any means. But I've been around racing enough to understand that unless you ARE an expert, relying on what race teams do is a dangerous business. Race teams tear down most race engines pretty often. AT the very least, they change spark plugs every race. Most consumers end up preferring not to swap out spark plugs every few thousand or ten thousand miles. If there is a platinum or iridium plug that actually works in the real world, doesn't harm the engine with a range that is too hot, and doesn't easily foul, it's likely a good choice. Factory specifications are there for a reason, but sometimes actual real-world results end up being a much better guide. And, while I haven't always taken all his advice, Jerry hasn't steered me wrong yet.

 

[KennethS]

Most consumers end up preferring not to swap out spark plugs every few thousand or ten thousand miles.

I'll agree with you, but I have never heard of anyone changing spark plugs that often. The manufacturers don't even suggest that.

 

[Jerry Bransford]

I'll agree with you, but I have never heard of anyone changing spark plugs that often. The manufacturers don't even suggest that.

Race teams do, that's about it and that's who he said replaces them that often. If they're serious competitors at the high end of the game nearly everything is replaced or rebuilt between races.