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Topic Review (Newest First)
12-22-2013 01:18 PM
Jerry Bransford Increasing the octane above what the engine was designed for will not affect its mpg in the least. In fact, the higher the octane, the harder it is to ignite and the slower it burns. If running a higher octane gasoline by itself improved fuel economy, you can bet Obama or the EPA would have long ago mandated its use.

I'm not making this up, even the EPA agrees with what I said here.
12-22-2013 01:09 PM
rmxauto
Bosch plugs bad, High octane good.

Quote:
Originally Posted by drivebytruckerz View Post
Just like it's love of 87 octane (simple) gasoline.. the Chrysler 4.0, as stated by pokey, are simple engines and are made to be maintained simply with simple, common parts. Just stick with the basics.
I've also had bad experiences with Bosch plugs. On 4.0 and other engines. I think it's because of the tiny center electrode. Any blowby or stem seal leakage will foul them in no time. First experienced this on a '68 Ford 302. Maybe they're OK on BMW or whatever, but on US made pushrod engines, no dice. For me, it's NGK, Denso or Champion all the way.

On a side note, in my experience 4.0s and lightly modded 258s both really like 93 Octane. 87 is OK, but I get almost 10% better fuel mileage using high-test. I wonder if this is unique to my vehicles and/or climate. I advance the timing quite a bit on the distributor models, and usually use platinum plugs.
10-10-2010 09:28 PM
bobsalmon Jerry is right. Higher octane in any low compression engine does nothing for performance. Keep using 87 octane. High octane is used to prevent detonation in higher compression engines. Using a higher grade fuel will just waste your money.
10-10-2010 07:41 PM
moscoeb Thanks, I got 23000, might explain why it occasionally idles slightly rough, looks like I got a(nother) project!
10-10-2010 02:48 PM
Jerry Bransford 25K miles is about as much as I'd trust conventional spark plugs, especially in a distributorless engine that will go through conventional plugs nearly twice as fast.
10-10-2010 02:42 PM
moscoeb So with the stock plugs, what mileage should I start to think about replacing them? 2006 4.0L. Distributorless.
10-10-2010 01:57 PM
Annapsmitty
Champion Truck Plug 4412

Just thought I'd throw this link out there:

ChampionSparkplugs.com - Cross Reference Search Results

Looks like it is true that the Champion Truck Plug (4412) actually has been discontinued.

Just an FYI
08-16-2010 02:38 PM
rrich I finished the rest of them this morning. I'd recommend everyone watch it - good information.

During one of the modules the guy said the 3 most important things are fuel, spark, and compression. My wife argued - "No! The 3 most important things are finding the keys, lipstick, and the cell phone."

I'm not so old and closed minded I can't try new things. I've had lots of bad experiences with plats - based on experience. Starting years ago when they first got popular I still had my dyno performance shops - sold the last one in '84. Every time, with no exceptions, plats always caused misfire and terrible running. We did not work on imported cars - they seemed to work OK in some of those. I would not stock plats, nor would I install them.
I tried them quite a few times using my dyno - even experimented with the heat ranges - all bad results.
But I don't remember what they were - possibly Bosch. I threw the Bosch rep out - I would not stock or use his junk.

My mainstay was Champions.

Champion was very good to me - when we'd build up a race engine I'd call the Champ Rep - he'd come out to my shop and use his equipment - pyrometers, internal cameras, etc to determine the right plug to use. Things like indexing, reach, and the heat ranges at low, med, and high speeds as well as heavy and light loads. He'd spend 2 or 3 hours on the dyno. In turn I let him use the dyno for some of his projects.

I'd think Jeep would understand the reasoning behind the double plats with waste spark ignitions. Why don't they call out plats on the underhood label?

Now in my limited business at home - (I thought I retired) - when it's been a misfiring problem and I found plats, trashcan time. Using the plugs called out on the label has always worked - when it was a plug issue.

But - after seeing the video - and years have passed since I became prejudiced - technology must have changed - I'll try a set in my Rubi.

You can teach old dogs new tricks - it's just more difficult.
08-16-2010 12:43 PM
Jerry Bransford
Quote:
Originally Posted by rrich View Post
Interesting - so far I've only had time to do module 6 - but I will do them all.

As both of us speculated a year ago, the misfire code for a particular cylinder is detected by that cylinder not contributing to the rotation. They showed a square wave pattern from the CPS - with a missing pulse. That's what the PCM is monitoring. I've seen that CPS pattern many times with my software, but I guess never with a misfire.

They said people expect more than 30K miles on a set of plugs, that's why the plats. My '03 Rubi new didn't come with Plats. It had what the label said.

I haven't worked on it for a while, but I'm still trying to make an adapter so a conventional scope pattern can be seen with the coil rail. It would be nice to see the scope pattern - it can tell lots of things at a glance.
It was module #1 that I especially wanted you in particular to see.
08-15-2010 11:16 PM
pokey
Quote:
Originally Posted by Jerry Bransford View Post
Take that spark plug and ignition course Motorking provided above Rich, you will be surprised at some of the information contained within it. Especially what plugs DIS engines require which of course includes the newer distributorless 4.0L engine. Especially in the #1 module that is only about 15 minutes long. I completed all six modules, it was worth the just over an hour it took.
Hey Jerry, was there any great revelation in that course ? I went to register but it seemed Autolite only wanted professional mechanics to take the course. The required fields included employers and managers names etc.
08-15-2010 10:25 PM
marc1kim My automotive teacher once told me when it comes to spark plugs, stick with OEM, all the high dollar stuff is just snake oil.
08-15-2010 09:40 PM
rrich Interesting - so far I've only had time to do module 6 - but I will do them all.

As both of us speculated a year ago, the misfire code for a particular cylinder is detected by that cylinder not contributing to the rotation. They showed a square wave pattern from the CPS - with a missing pulse. That's what the PCM is monitoring. I've seen that CPS pattern many times with my software, but I guess never with a misfire.

They said people expect more than 30K miles on a set of plugs, that's why the plats. My '03 Rubi new didn't come with Plats. It had what the label said.

I haven't worked on it for a while, but I'm still trying to make an adapter so a conventional scope pattern can be seen with the coil rail. It would be nice to see the scope pattern - it can tell lots of things at a glance.
08-15-2010 06:58 PM
Jerry Bransford Take that spark plug and ignition course Motorking provided above Rich, you will be surprised at some of the information contained within it. Especially what plugs DIS engines require which of course includes the newer distributorless 4.0L engine. Especially in the #1 module that is only about 15 minutes long. I completed all six modules, it was worth the just over an hour it took.
08-15-2010 06:19 PM
rrich Under the hood, top of the firewall, driver's side - a white label - it tells what plugs that particular engine was designed to use. Not all 4.0's are the same, some are different, due to small head changes etc.

Bosch and many of the others - especially many of the "trick performance plugs" go by "one size fits all." If it fits the hole, they say to use it. Just because a plug that's designed for a Yugo fits the hole it doesn't mean it's the right one. Ask your wife how "one size fits all" fits her.
08-15-2010 04:50 PM
frazier
Quote:
Originally Posted by cru9 View Post
Did you do the plain jane AP985?
No I just went with plain 985's The AP985 will be the wrong plug, the APP985 would however work. Jerry gave me the info and I can't believe how much better it runs. This site is great, especially if you're a first time Jeep owner like myself.
08-10-2010 09:00 AM
motorking
Spark plugs

Quote:
Originally Posted by sbregister34 View Post
I always recommend to use the OE plugs at my shop. Always had problems when varying too much in plugs.
The reason for that is some maunfacturers do a great job matching heat ranges, some do not. I work for Autolite so I am not going to name the names of those who do not! We make OE plugs under several brand names. That said, an engine doesnt have any idea what brand of plug is in it, it only knows if its good or not. We work very hard to match OE heat ranges and never have a problem. If any of you would like to learn more about spark plug metalurgy, heat ranges, DIS and other ignition systems, go to Autolite Challenge Professional Technician Program: Home Page. Register and watch the videos #1 and #5. If you watch all six and answer the questions by august 31st, you will win a free Carhart jacket.

08-09-2010 06:40 PM
Ted_D stopped in several places today and couldnt find a single Autolite APP985. NAPA ordered them and said they would be in 7am tomorrow. They tried and tried to sell me something else but I told them I would just wait.
08-09-2010 06:34 PM
sbregister34 I always recommend to use the OE plugs at my shop. Always had problems when varying too much in plugs.
08-09-2010 05:00 PM
Jerry Bransford
Quote:
Originally Posted by Wrangler97-EEK View Post
You say nothin more than 87 octane? My 97 is not adjustable on timing and idles at 17 degrees btdc. You can tell the difference between 87 and 92.
The TJ's engine will not run any differently with 87 vs. 92. Really, aside from a possible Placebo Effect.

There is no knock sensor in the 4.0L engine so there is nothing in the computer that could advance the timing to take advantage of a higher octane, even if the engine's compression warranted use of a higher octane which it does not.

Trust me, your engine isn't running any differently with 92 octane. In fact, in an engine without a knock sensor to help with the engine timing, running a higher octane than the engine was designed for can even leave deposits in the combustion chambers behind. That is because higher octane gasolines are not as easily ignited and they are slower burning than a lower octane gasoline.

By itself and without an engine designed to run a higher octane, an engine will run no differently and have no more power or run more cleanly than a similar engine running the standard level of octane it was designed for.
08-09-2010 04:51 PM
Wrangler97-EEK You say nothin more than 87 octane? My 97 is not adjustable on timing and idles at 17 degrees btdc. You can tell the difference between 87 and 92.
08-09-2010 02:44 PM
pokey
Quote:
Originally Posted by cru9 View Post
Did you do the plain jane AP985?
The plain jane is the autolite 985 (no letters in front). The P in AP stands for platinum. The 985's are copper. Cost about a buck each and the 4.0's love 'em. You should change them at 25 or 30K which to me is no big deal because there's something about changing my plugs that I enjoy.

The platinums will last a lot longer, but like I said, the 4.0's love copper plugs. Another good copper plug (the one I use) is the Champion 4412 truck plug. Kragen/O'reilly will tell you they are discontinued but they are not. Call around. Carquest has them. It was explained to me they call them truck plugs because they're a heavy duty plug. Cost more than a buck, but great plugs.
08-09-2010 12:34 PM
Jerry Bransford
Quote:
Originally Posted by Big O View Post
Using Mid-grade fuel.
There is zero... nada, none whatsoever, benefit to using a mid-grade octane fuel in our TJ engines. Using any octane higher than 87 is just costing you more $$$ without any benefit whatsoever. 89 doesn't provide any more power or cleaning additives than 87 does. The only thing octane does is to slow how quickly the fuel ignites and to prevent premature compression-induced ignition in high compression engines... which the 4.0L engine is not. Really.

P.S. Here's a slightly longer explanation of why running a higher octane fuel than the engine was designed to require doesn't help... http://www.wranglerforum.com/f5/gas-...tml#post715509
08-09-2010 11:38 AM
Rykugb
Quote:
Originally Posted by Big O View Post
Installed the Platinum Ir Fusion a few weeks ago and the engine is running smooth. Gained 1 MPG. Using Mid-grade fuel.
F!!! I have been using the same set up for over 2000 miles with a steady performance loss since. I thought the coil packs were starting to go because of start off hesitation. I guess I have a project tomorrow.......
08-09-2010 11:17 AM
pokey
Quote:
Originally Posted by motorking View Post
Use the Autolite XP985 dudes! This is a iridium fine wire center electrode with a pltinum button on the side wire. less volatge to fire, bigger flame kernal and 100k durability. You will notice a difference in the way your Jeep runs.
It works good in spaceships too....
08-09-2010 08:24 AM
motorking
What is the best plug for a DIS 4.0 Jeep?

Quote:
Originally Posted by Big O View Post
Installed the Platinum Ir Fusion a few weeks ago and the engine is running smooth. Gained 1 MPG. Using Mid-grade fuel.
Use the Autolite XP985 dudes! This is a iridium fine wire center electrode with a pltinum button on the side wire. less volatge to fire, bigger flame kernal and 100k durability. You will notice a difference in the way your Jeep runs.
08-02-2010 11:30 AM
Big O Installed the Platinum Ir Fusion a few weeks ago and the engine is running smooth. Gained 1 MPG. Using Mid-grade fuel.
08-01-2010 06:58 AM
cru9
Quote:
Originally Posted by frazier View Post
Thanks Jerry, I removed the Bosch plugs and went with Autolite 985, just plain old plugs and I can't belive the difference it made.

Thanks again for the info!

Frazier
Did you do the plain jane AP985?
07-31-2010 05:21 PM
frazier
Autolite plugs

Thanks Jerry, I removed the Bosch plugs and went with Autolite 985, just plain old plugs and I can't belive the difference it made.

Thanks again for the info!

Frazier
07-23-2010 01:11 AM
Jerry Bransford
Quote:
Originally Posted by frazier View Post
They are the Bosch Platinum Plus plugs, part number 4003, does that help? Nothing on the box mentions single or double tipped paltinum.
From the description at Bosch Spark Plugs: Automotive spark plugs, Motorcycle sparkplugs, high performance plugs the 4003 is a single-tipped platinum plug with platinum only on its center electrode. That's the wrong type of plug for your newer TJ and while it may run ok for now, single-tipped platinum plugs inevitably cause problems in the newer distributorless 4.0L engines later on. For the newer distributorless 4.0L engine which uses what they call a "waste-spark" ignition system, both sides of the spark plug gap must be made from the same material.
07-22-2010 09:00 PM
frazier
Quote:
Originally Posted by Jerry Bransford View Post
If they are not Plus 4 or Plus 2 plugs which are both bad, they may or may not be ok. Do you know if what you installed are single or double tipped platinum? If you don't know, what model # plug did you install?
They are the Bosch Platinum Plus plugs, part number 4003, does that help? Nothing on the box mentions single or double tipped paltinum.
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