Kymasabe

OK, I've read a bunch of info on spark plugs and it's about as hotly contested as "whats the best oil".
I'm not going to ask "what's the best spark plug" because that question's not accurate. So, here's what I'm looking for.
What is the most reliable spark plug for an '04 WJ, 4.0 liter with the coil pack thing on the plugs.
I don't care if I have to replace them every 30k miles, so if simple copper core is the most reliable choice, then great. I've heard Bosch is great, then another says Bosch sucks. I hear E3 is great, then another says their's ran like crap and was throwing codes until they went back to simple copper core.
I hate having to pull the coil pack, much prefer the cap, rotor and wires on my XJ so I only want to do this once.
I bought 6 NGK V-power plugs a year ago, don't remember why, but now not sure I want to use them. Don't know if NGK is good choice or if Champion would be better.
I hear too many horror stories about iridium and platinum and all those. I like simple, and time tested.
What's out there that your using that works? Every time. Reliably.
Oh...and what's the correct gap for our 4.0's? .035?

SteveMongr

The 4.0 motor does not like fancy plugs. Standard resistor-type, copper core work best. Good info in the following links.
Standard resistor-type for WJ 4.0
P/N SP0RC12ECC
(formerly 56041402AB)
Type: RC12ECC
0.035 in. gap

http://www.wjjeeps.com/service/sparkplugs.htm
http://www.wjjeeps.com/engine.htm

dave1123

I've been using NGK ZFR5N (3459) in my 2000 with good service, even with high mileage oil consumption.

My job requires waiting for usually about 2 hours in a parking lot before I get my newspapers. If I don't get there early, I'm late getting started on my route. This causes me to idle for long periods in the winter just to stay warm. The Champs I was using will carbon up after a while and misfire. The NGK's will blow clean after I hit the highway. She's got 232K miles on her.

97grand4.0

Don't forget to torque them to book spec.

Kymasabe

I don't have a FSM...what is the correct torque spec ?

97grand4.0

There is this thing they have ...called google...you can search your own stuff for something as simple as a spark plug torque. But I think it's around 22 ft.lbs.

SteveMongr

The simple stuff like Spark plugs, tune up specs, all fluid types and capacities are found in the owners manual, sticker on driver door or sticker in engine bay.

inShane

OEM plugs are Mopar® P/N SP000ZFR5N, 0.035 gap. I just picked up 6 of them on ebay for a little over 30 bucks.

inShane

Here is a good reference for many things, I'd also recommend an owners manual.
http://www.wjjeeps.com/service/maintenance_wj.htm#ENGOIL

Kymasabe

Since you mentioned the torque spec, I thought I'd simply ask if you had the spec. If I'd known it came with a healthy dose of sarcasm, I wouldn't have bothered.

dave1123

Okay, chill out. We get so many simple questions like this it's hard NOT it get sarcastic. Sometimes we get questions it's like you know the guy hasn't even opened the hood!

BTW, my owner's manual specifies Champs, but I've found IGKs last longer and run cleaner. They are also specified for later model 4.0s.

I've been working on cars for 60 years and I've very seldom torqued plugs. Only with tapered seat ones. Gasketed plugs you just crank them until you can feel they have crushed the gaskets completely, then stop. I've never had one loosen up. BUT I'm a dinosaur!

97grand4.0

Thanks, Dave. To be honest I never torqued them either , until a few months ago, when I got a nifty Harbor Freight 3/8" torque wrench.
I put it on a new set, and discovered I could crank them ALL about another 2 turns beyond what I THOUGHT was tight.

Not to hijack the thread too badly but I was talking to a machine shop owner about doing my head, turns out I went to the same boces machine class of 77 with him. He says most heads from jeeps he gets are warped, he thinks it's because when they are Removed, the bolts are not done in reverse sequence. 3 angle valve job with .0005 runout, $220. Mill head $150.

dave1123

He's got a point! That used to be a real problem with the flatheads. I've seen guys use an impact wrench to remove heads and that freaks me out!