New spark plugs make a big difference!


Jerry Bransford

TJ Guru Moderator
Staff Member
Supporting Member
Joined
Nov 9, 2015
Messages
16,502
Location
Escondido California
Watched a youtube video about changing plugs. Suggested putting motor oil on the threads. Cant say I agree with that. Maybe some Anti-seize?
Gotta be careful with Youtube videos, many are just idiot amateurs giving bad advice.

If you put antiseize on the threads, just make sure to only put a very small amount onto the threads and make sure none of it can get onto the electrodes during the install. Antiseize is conductive so it will really screw things up if it gets onto the electrode.
 

CharlesHS

TJ Addict
Supporting Member
Joined
Mar 10, 2020
Messages
1,740
Location
Jacksonville, FL, Quezon Philippines
Champion are the suggested OE brand, correct?

As far as 3.73’s and your 33’s, do you have an auto or manual trans? Im currently on 3.73’s w an AX-15 and have no complaints. Maybe Im just accustomed to it. I just recall when I had 29” tires, my shift points were really quick. Wasn’t a fan. Im sure had I crawled back then, it would have been more enjoyable, Id guess.


Sent from my iPhone using Tapatalk


This topic has been discussed ad nauseum; I am sure I will receive numerous negative comments, but here goes.
While some members recommend the iridium, some recommend the double platinum tipped and others recommend the standard plugs.
Shortly after purchasing my '01 4.0L I replaced the OLD NGK ZFR5N factory recommended plugs with the platinum tipped plugs recommended on the forum. Within less than a week my engine was throwing codes for random misfires on all cylinders. I pulled the plugs and really didn't see a problem so I went up to a friends house who was a Jeep dealership mechanic for almost 30 years.
He connected the factory diagnostic tool to the OBD2 port, revved the engine to around 1800 rpm's for 200 seconds and registered over 200 misfires on most of the spark plugs.
I told him that I had inspected the plugs and didn't see any thing obvious, but he pulled them any way. Upon pulling the first plug... he asked who put these platinum tips in; the factory recommends the ZGK ZFR5N ?
He explained to me that around 2001 the dealers were having a lot of problems with reported misfires on new vehicles along with explaining the waste spark idea and that after extensive research the factory found the problem to be the platinum plugs. Apparently a lot of vehicles have problems, but some don't.
He pulled the platinum plugs out and installed the NGK's and 95% of the misfires went away; after performing a combustion chamber cleaning the other 5% went away and the codes were gone.
Another diagnostic test was performed for 200 seconds and in that time there was only 1-2 misfires on two cylinders; I add Seafoam cleaner to my fuel once a month and the problem has not returned.
This has worked for me...
 
Last edited:
  • Like
Reactions: driftless

TDB55

TJ Enthusiast
Supporting Member
Joined
May 18, 2019
Messages
287
Location
North Carolina
Per Autolite’s Website:

NOTE: Spark plugs should be installed with clean and dry threads to avoid over-torqueing. This can distort the metal plug shell, which often results in engine damage.

Also:
There is a debate whether or not to use anti-seize when installing spark plugs.
  • No longer necessary as modern spark plug coatings work as a releasing agent and should be installed dry
  • Anti-seize can alter the tightening torque up to 20%, increasing risk of breakage
  • Anti-seize can create heat transfer and electrical conductivity concerns
  • Only use anti-seize where it is OE recommended
 

Stretch

TJ Enthusiast
Joined
Jul 22, 2019
Messages
149
Location
Alberta
I went to the parts desk at my local Jeep dealer and asked for whatever was meant for my Jeep... got a box of ngk labelled mopar nickel plugs for $10 ... installed them dry (no oil or anti seize)
23E9B932-EEAB-40DA-9FBA-ADE3A1356A46.jpeg
61FD436A-10A6-4460-9DAA-96F5829F42AB.jpeg
 
  • Like
Reactions: CharlesHS

Fonz54

TJ Enthusiast
Supporting Member
Joined
Apr 9, 2018
Messages
796
Location
Monterey, CA, USA
They are one good brand, I like Autolite too as the other brand.

Know that because your 2001 has the coil rail ignition system that it is fussy about what spark plugs it likes to run well on. There are three plugs I recommend for newer 4.0L engines likes yours. These first two are good for 100k miles... Champion 7412 or the Autolite APP-985. Both of those are double-tipped platinum (platinum on both sides of the gap).

Do NOT install the Champion 3034 or Autolite AP-985 in to newer coil-on-rail 4.0L engines which are single-tipped platinum plugs (which are only suitable for the older 4.0 engines with a distributor cap). Single-tipped platinum plugs will eventually cause misfires and/or a rough idle in newer coil-on-rail 4.0 engines. Single tipped means the platinum is on just one side of the gap.

Or the Autolite XP-985 which is iridium tipped. This is what I run in m '04 4.0L engine, it's good for 200k miles and it's suitable for use in any of our 4.0L or 2.5L engines.
I just replaced the APs in my ‘04 with XPs. Runs smoothly and starts right up as opposed to cranking for a few seconds before firing with the old plugs.
 

Zorba

"The Veiled Male"
Supporting Member
Joined
Apr 2, 2020
Messages
2,455
Location
Merritt Island, Fl
I just replaced the APs in my ‘04 with XPs. Runs smoothly and starts right up as opposed to cranking for a few seconds before firing with the old plugs.
I put XPs in mine too. A very slight/subtle stumble at idle went away. The old plugs were probably the originals!
 

CharlesHS

TJ Addict
Supporting Member
Joined
Mar 10, 2020
Messages
1,740
Location
Jacksonville, FL, Quezon Philippines
  • Like
Reactions: Stretch

TheBoogieman

Disturbed Jeepaholic
Supporting Member
Joined
Jan 1, 2019
Messages
1,104
Location
CharlottesHELL, Va
I have used Autolite plugs in all 18 of my Jeeps, never had any issues (except better gas mileage from replacing worn out copper plugs), never used anti-seize and have never over torqued them. I use Iridium, except for my 98-99' Jeeps that I used the Autolite AP-985 plugs.
 
Last edited:

WallyWest

TJ Enthusiast
Joined
Nov 6, 2019
Messages
946
Location
PA
Every car forum I've been on has this argument.

As long as the plug conforms to factory specs in terms of making good spark with the supplied voltage it will work. Using double platinum or iridium is just so you don't have to change them as often. Recommended for waste spark engines just because they eat standard copper plugs for breakfast. You'll get 30k miles max on copper, probably should change them at 20k. I know, people run them much longer. Those are the ones that comment on how much better it runs when the finally change them, and credit the new fancy plugs they bought. No, they aren't magic plugs, you were just driving very worn out plugs that made your engine run like crap.
 

TheBoogieman

Disturbed Jeepaholic
Supporting Member
Joined
Jan 1, 2019
Messages
1,104
Location
CharlottesHELL, Va
I went to the parts desk at my local Jeep dealer and asked for whatever was meant for my Jeep... got a box of ngk labelled mopar nickel plugs for $10
They obviously wouldn't tell you to buy plugs that they don't sell. There are much better options. Everybody can buy what they want because it's their Jeep.
 

Jerry Bransford

TJ Guru Moderator
Staff Member
Supporting Member
Joined
Nov 9, 2015
Messages
16,502
Location
Escondido California
I went to the parts desk at my local Jeep dealer and asked for whatever was meant for my Jeep... got a box of ngk labelled mopar nickel plugs for $10 ... installed them dry (no oil or anti seize)
The problem with parts counter sales people is they're only there to sell parts, they're not technically astute and they're not up on which plugs work best in all situations. Of course the NGK plugs they sold you work but what they didn't advise you on, because they don't know, is that your engine has a "waste spark" ignition system that fires the spark plugs exactly twice as often as a standard ignition system does. That means it goes through conventional plugs twice as fast as the same plugs would last with a conventional non-waste spark ignition system.

If the parts counter guy had been educated about waste-spark ignition systems he likely would have advised a platinum plug with the platinum on both sides of the gap (due to the waste spark ignition design) like the Autolite APP-985 or an iridium like the Autolite XP-985.

In other words, just because a parts salesman says it will work, it doesn't necessarily mean he's giving you what is the best choice for your engine's waste spark ignition system. Will that conventional NGK plug you installed work? Of course. But with your waste-spark design firing twice as often it will likely last about 1/5 as long as the correct platinum and 1/15 to 1/20 as long as an iridium would.

And do all Jeep engines have a waste-spark ignition system? Nope, and neither did my '97 TJ with its 4.0 engine. The waste-spark ignition system showed up on the 4.0 around 2000.
 
  • Like
Reactions: Zorba

Buckeyebutch

Member
Joined
Aug 29, 2018
Messages
60
Location
OHIO
Per, Jerry ( The waste-spark ignition system showed up on the 4.0 around 2000. )
I have a 2000 so how do I determine if my 4.0 is a waste? LOL
 

freedom_in_4low

TJ Addict
Supporting Member
Joined
Sep 26, 2019
Messages
1,486
Location
Monument, CO
I thought there was no way to feel a power difference with a spark plug change. I put in a set of iridium today, and by gosh I do feel a noticeable difference. Who knew?

No way if the first set of plugs are the correct ones and in good working order.

Mine had gaps well over 0.070 and new plugs made no difference whatsoever.
 

freedom_in_4low

TJ Addict
Supporting Member
Joined
Sep 26, 2019
Messages
1,486
Location
Monument, CO
Per, Jerry ( The waste-spark ignition system showed up on the 4.0 around 2000. )
I have a 2000 so how do I determine if my 4.0 is a waste? LOL
If you have multiple coil packs on the passenger side, you have a wasted spark distributorless ignition. If you have a distributor, you don't.
 

tony e

New Member
Joined
Dec 24, 2019
Messages
8
Location
31788
Ok per Jerry's recomendation (because I feel like he's the Jeep Guru) I ordered the XP985's. Going into a 04 4.0 /123k on the clock. I've owned the Jeep for 4yrs. Got them installed and Jeep fired instantly. My normal cranking procedure was spin it for 3-4 seconds. Knew it wasn't gonna fire. Hit it again & it cranks. The plugs I pulled out were NKG ZFR5N.
I can only assume that the were factory installed. Gaps were from .075-.080 had 1 that was close to .090.
Hard for me to believe this thing even cranked. Ain't took a test ride yet but thus far I'm happy.
 
  • Like
Reactions: TDB55

bstrobel64

Member
Joined
Jun 1, 2020
Messages
48
Location
Fort collins
Per, Jerry ( The waste-spark ignition system showed up on the 4.0 around 2000. )
I have a 2000 so how do I determine if my 4.0 is a waste? LOL
Hopefully this helps. Top is distributor, bottom is distributorless (waste spark). Look at the passenger side of your engine. These are both pictures of Jeep 4.0's.

JeepCherokeeDistributor_02.jpg


step2.jpg
 
  • Like
Reactions: TDB55