4.0L Ignition upgrades....{searched on 'ignition' first};D

[mbryson]

Kartsman's question about his erractic running TJ has me thinking of things on the 4.0L ignition system as I've been having similar problems that are normally cured by changing plugs. I'm gapping to .040 rather than .035 as suggested, but I do the exact same thing in the ZJ {4.0L } with absolutely no problems.

Anybody ever have any real luck with an aftermarket coil on a 4.0? Some people swear by the Jacobs stuff and some really hate it and think it's a waste. I've only got experience with aftermarket ignition stuff on big V8 engines and was curious how that affects these little dudes.

The master question. Is there an equivilent HEI 'silver bullet' for our little sixes {so they're kind of big for a six, OK--they're still under 6.6L}?????

[Jerry Bransford]

What kind of plugs are you running? I've had great luck with Autolite single-tipped (double-tiipped platinum is only for distributorless 4.0L engines) platinum plugs, getting 60K+ miles out of them. With older Jeeps, I believe aftermarket ignitions can do wonders. With newer 4.0L engines, I think the factory ignition is good enough that aftermarket systems like made by MSD and Jacobs are a waste of money.

Jacobs? I think they are nothing but overpriced and over-hyped waste of money and that their commissioned salesreps will promise you anything you want to hear to get the sale. It's also like pulling teeth to get them to honor their advertised policy on refunds if you don't get the promised performance. I'd buy an MSD ignition if I had an older vehicle but I wouldn't touch Jacobs with a ten-foot pole.

[mbryson]

Originally posted by Jerry Bransford
What kind of plugs are you running? I've had great luck with Autolite single-tipped (double-tiipped platinum is only for distributorless 4.0L engines) platinum plugs, getting 60K+ miles out of them. With older Jeeps, I believe aftermarket ignitions can do wonders. With newer 4.0L engines, I think the factory ignition is good enough that aftermarket systems like made by MSD and Jacobs are a waste of money.

Jacobs? I think they are nothing but overpriced and over-hyped waste of money and that their commissioned salesreps will promise you anything you want to hear to get the sale. It's also like pulling teeth to get them to honor their advertised policy on refunds if you don't get the promised performance. I'd buy an MSD ignition if I had an older vehicle but I wouldn't touch Jacobs with a ten-foot pole.

Sorry, that would probably help if I'd post exactly what I'm having problems with. Sheeessshhhh, picky, picky, picky....didn't you read my last related post to Kartsman's subject.....j/k....


I've run Champion plugs {OE} as I got about 60K out of the stockers in the ZJ. My experience has been that the aftermarket Champions are not quite as 'cool' as the Chrysler stockers. I got mad and put a set of Autolites in the ZJ after losing a set of Champions after about 6K or so, and then tried the Champions in the XJ. Same results. I'm running the Autolite {as of last night} in the XJ as I got the poor running symptoms after about 2K. Miracle cures to the ignition system, those spark plugs.

I thought we'd get the Jacobs endorsers on here, and I'll take those with a grain of salt, as I've never had anything other than a GM HEI be the 'silver bullet' in regard to ignition systems. I just don't know of a 'silver bullet' for the mighty 4.0L and hoped to get some discussion going on the subject.

[karstman]

Marc,
Check my other thread
I think I found it and it's not ignition related.

I agree 110% on the big and small V8's. On my supercharged SBC, I run all MSD and Taylor. On the jeep, I run Champion truck plugs (4412?) and the rest is all Mopar. It's reliable, affordable, and it works. At least that has been my experience. 96,000 miles, 2 trips to Colorado, 1 trip to Moab, and one to go This latest problem is the first burp the motor has given me in almost 4 years.

later,
Mark

[mrblaine]

No Jacobs endorsers here or any other aftermarket crap that supposedly can out do stock in the OBDII monitored systems.

I do think that Jerry garners large amounts of delight from making me follow him around and continually offer up the challenge to him to bring his plugs up and put them in my rig. I have a 99 and first on a whim and with more determination later on, have tried just about every aftermarket upgrade to some portion of the ignition, induction, and exhaust system that I could afford. I can afford quite a bit when I get cranky.

Not one thing that I did, plugs, ultra super duper solid core wires, high flow cat, high flow exhaust, high flow intake, wowie bango spark plugs, bigger throttle body, nothing had any lasting effects, and I still challenge anyone with a dyno to prove me wrong.

I have a 99 just like mine we can do all testing on. I'll pay for every add on and the dyno run that lasts for longer than a month of normal driving and you pay for the ones that fail to perform as adverstised. Any takers???

Normal aspiration only. I do believe with a fair bit of tinkering I could get a supercharger to work, but I'm not sure why I would want to.

Here is my experience. I bolted them all on one at a time. There would be noticeable improvement for about a week and a half. Then it would go back to stock performance. How do I know?

We used to drive the toll road to Big Bear every week and the reason I was doing the mods was to hit the toll booth at the top of the last hill doing faster than 60 miles an hour floored.

I would do a mod and go test it on that hill. All of them except for the exhaust would get me up the hill the first time without the dreaded downshift. No other changes and hit the hill a week later. Back to stock and stock performance levels after a week or two of normal driving.

[TJRON]

Aww, c'mon Blaine, are you saying you didn't get any "seat of the pants" performance gains with all that cool stuff?
I'm running a K&N and I swear I can feel the performance gains every time I get in the rocks. I also think I picked up a few horsepower when I put synthetics in my tranny. One thing I am sure of: The engine runs smoother after I wash and vacuum the Jeep out real good.
Ron

[Jerry Bransford]

Originally posted by mrblaine


I do think that Jerry garners large amounts of delight from making me follow him around and continually offer up the challenge to him to bring his plugs up and put them in my rig. I have a 99 and first on a whim and with more determination later on, have tried just about every aftermarket upgrade to some portion of the ignition, induction, and exhaust system that I could afford. I can afford quite a bit when I get cranky.

Not one thing that I did, plugs, ultra super duper solid core wires, high flow cat, high flow exhaust, high flow intake, wowie bango spark plugs, bigger throttle body, nothing had any lasting effects, and I still challenge anyone with a dyno to prove me wrong.

Oh heck Blaine, I have never claimed I could feel any performance or fuel economy differences with the single platinum-tipped Autolite plugs I like to use in my '97. I only recommend them because my 4.0L runs smoothly with them and I get way over 60K miles on a single set of plugs. The last time I checked them with over 60K miles on them, they were still in great condition. The plugs I love to bash are Splitfires and Bosch Plus4 plugs! I did run Champion Truck plugs for around 15,000 miles while I was troubleshooting a misfire problem that I think has been traced to a bad batch of weak valve springs (there's a TSB on it), and there was no performance difference (not that I expected any) between them and the Autolites.

[brent]

marc, I've got an old jacobs kicking arround if you want to try it, its in the top of the garage somewhere