Jeep Wrangler Forum banner
  • Hey everyone! Enter your ride HERE to be a part of September's Ride of the Month Challenge!
1 - 19 of 19 Posts

·
Registered
Joined
·
99 Posts
Discussion Starter · #1 ·
Yep, there's tons of info on here about what's the best plug to run in the 4.0's. After reading just about every thread out there pertaining to them, I bit on the Autolite APP985's and wow, what a difference! New plugs had to be re gapped due to the knucle head at the parts store throwing them around on the counter (I had to ask him to be careful eventually). As I pulled an old plug and replaced it, I checked the gapping on the old ones too. Not a single plug was less than .065!!! Can't believe she would even crank. It's yet another testament to how tough these 4.0's are. Immediate improvement in idle, throttle response and, dare I say, she's got a little more pep to her now. For $4.56/per, I'd say it was great Sunday afternoon project/investment.
 

·
Registered
Joined
·
522 Posts
I just switched from NGK to Auto lite double platinum and noticed a different right away.
my gap were close to what yours were in my old plugs,caulk it up to wear.
 

·
Premium Member
Joined
·
153 Posts
I put in Autolite XP-985 plugs about a month ago, the Jeep was running well before the change but running noticeably better after. I carefully gapped them and followed all the good instructions we have on this site and was definitely rewarded.

Many thanks to all who share information on the Forum !
 

·
Registered
Joined
·
4,307 Posts
Old, worn-out plugs of Brand X get replaced with new plugs of Brand Y.
Engine runs better.
Conclusion: Brand Y is so much better than Brand X.

The average fifth-grader should see something wrong with that picture.
 

·
Registered
Joined
·
1,487 Posts
New plugs had to be re gapped due to the knucle head at the parts store throwing them around on the counter
Whenever you install new spark plugs, you should always check their gap first. Even if they were gently packaged by the blind nuns of Tuscany, their gap can and will vary from plug to plug.

FYI
 

·
Registered
Joined
·
4,307 Posts
Whenever you install new spark plugs, you should always check their gap first. Even if they were gently packaged by the blind nuns of Tuscany, their gap can and will vary from plug to plug.

FYI
Not only that, but a particular plug is often used in a variety of applications which do not share the same gap specifications.
 

·
Registered
Joined
·
99 Posts
Discussion Starter · #8 ·
tangofox007 said:
Not only that, but a particular plug is often used in a variety of applications which do not share the same gap specifications.
Surprisingly, they were all fairly close to .035. I just found it comical that the parts guy tossed them around like a bag of bolts. But yes, I always make sure they're gapped correctly prior to installation.
 

·
Registered
Joined
·
1,385 Posts
tangofox007 said:
Old, worn-out plugs of Brand X get replaced with new plugs of Brand Y.
Engine runs better.
Conclusion: Brand Y is so much better than Brand X.

The average fifth-grader should see something wrong with that picture.
Did u find that information helpful?
 

·
Registered
Joined
·
99 Posts
Discussion Starter · #10 ·
tangofox007 said:
Old, worn-out plugs of Brand X get replaced with new plugs of Brand Y.
Engine runs better.
Conclusion: Brand Y is so much better than Brand X.

The average fifth-grader should see something wrong with that picture.
Never said anything declaring Autolites as the best of the best. Just that the simple change had improved my engines performance and that I was happy with them. It's fairly common sense that replacing worn out plugs is beneficial...just like replacing a dead battery will help it crank. As I use this forum for listening to peoples opinions for "what's working for them," I like to return the favor when applicable.
 

·
Registered
Joined
·
27 Posts
Has anyone noticed a drop in gas mileage after installing these plugs or is it just me? TJ runs great and noticeable pep. Or is it because I have more pep and now I am driving it like a race car? (reason for gas mileage)
 

·
Registered
Joined
·
99 Posts
Discussion Starter · #12 ·
muddybuddy said:
Has anyone noticed a drop in gas mileage after installing these plugs or is it just me? TJ runs great and noticeable pep. Or is it because I have more pep and now I am driving it like a race car? (reason for gas mileage)
As a matter of fact, I have. It doesn't seem to be much, and I'm guessing by the amount of times I'm filling up, compared to before, on a regular work week. I didn't do any accurate readings of mpg prior to installation but it definitely seems like I'm getting less miles between fill ups. I'm not counting out the increased aggression of driving though, it could very well be the reason :)
 

·
Registered
Joined
·
14 Posts
Mine threw a misfire code right before I left for the weekend to attend the GA-FL game (had to throw that in there given the OPs name and signature). I think the code was P0300, but I could be mistaken. Pulled out the worn out E3s installed by a previous owner and went for the APP985s myself and the difference was amazing. They were definitely overdue for a change.
 

·
Registered
Joined
·
132 Posts
I just changed out the spark plugs in my 1999 4.0. It had old Champions in it. I installed some new Champion 3034 plugs.

When I removed the old plugs they were clearly showing their age and somewhat larger gaps. But the gaps weren't huge.

I read a few spark plug threads on here and noticed several folks had noticed an improvement in power. I didn't really expect much change, but it was time to change them.

After the change I did notice the engine felt like it had more low end torque. It's nicer to drive in traffic now. A bit of a surprise to me. I've never noticed such a difference with just a spark plug change, in what seemed like an already proper running engine before the change. :cool:
 

·
Registered
Joined
·
90 Posts
I'm about to give my TJ a bit service and change the spark plugs. Don't think i can get auto lite plugs down here in NZ though. So might have to go with NGK iridiums

Cheers
 
1 - 19 of 19 Posts
Top