OK, It time for a tune up on my 98 XJ, 4.0. I was wondering what do you guy think the best brand to put in it. The first tune I gave it I tried the Bosch Platinum. And I ended up changing the out about a month later. The made it run really bad and had some bad fouling and like I said that was in just a month. I did replace them with Champion and it did run much better. I just want to see if you guys had a better experience with any other brand?
Thanks

 

When ever i get a used car i buy Denso Iridium Plugs. They go for about 15 bucks a plug but it is the last plug i will change in that vehicle for 100K miles.

 

regular copper plug, we don't have a high energy system and copper is perfect and the Jeeps love it. $2 plugs should last about 30k.

If you want to see some bad plug stories try a search

 

Up to 99 use Champion copper plugs. 00-01 use NGK copper plugs due to the change to a distributorless ignition system.


I've tried numerous plugs over the years and always go back to the basics because neither of my 4.0's like the fancy platinum, iridium, 2,3,4 element plugs.

 

I find it funny that you had an issue with Bosch Platinums. I've been using them in all of the XJs we have had or do have and all of them (a '95, two '97s, and the '98) for the last 12 years run great on them and they lasted a long time. I've used Autolite Platinums once and the engine liked them also. Personally, I'll stick with what worked for me.

I've never used Iridium plugs because of the high cost and the good luck I've had with platimuns. I've heard good things about them, though, but in 4 bangers and performance engines. I'm not sure if the higher cost will equate to anything much in our 6s.

I also don't believe in leaving plugs in for 100,000 miles despite the claims. It works for some people. I guess I'm just too old school.

 

champion copper 438 gapped at .035

 

Agree completely. Champion coppers for your 99.

87-99: Champion copper

00-01: NGK copper

And be darn sure to GAP them before installing them. .035. Never trust that the gap is correct right out of the box. Sometimes it is, sometimes it isn't. Don't take the chance for the amount of time it takes to verify the gap!

 

I remember reading in a classic car magazine that platinum plugs tend to cause cold start problems in older, low energy ignition systems.

 

I have used the Bosch in all me vehicles too and that's why I tried them in my Jeep. The one time I put them in my XJ it didn't like them.

Thanks for the comments and I think I will keep running the champion plus.

BTW, I do agree with you wjnfirearms. I also don't believe in running plug for 100,000.
Thanks again.

 

Championn copper plus run the best in the 4.0

 

Different engines like different plugs. I think I used champions. I know they are platinum though. I love'em. The plugs that were in before were autolites and fricked tires plugs took them out of the box and just put them in. I checked the gap and it was .050"! It ran surprisingly well though.
Anyways, plugs are more personal preference

 

Most plugs will run good at first but the Champions will lst a lot longer then the others in a Jeep. Champions are made by Mopar and designed just for your motor unlike the others.

 

What does the underhood sticker say?

Don't you think the engineers that designed it knew what they designed it to use?

BOSCH - HITLER'S REVENGE

 

DUH!
Champion is owned by Federal-Mogul Corporation, not MOPAR!

 

I've had Bosch Platinums cause driveability problems in a Honda CRX and an Alfa Romeo. Switched to NGK and problem solved.

The issue with 100,000 mile plugs that has come to light in recent years is that they like to pull the threads out of the aluminum heads cuz they haven't been moved for so many miles. We used to maintain a budget truck fleet. The recommended interval for plug change was 96,000 miles. I dreaded it cuz you were very likely to pull a spark plug and have the threads pull out of the head with it.