JamromXJ

Thanks to following some great how-to's and conversations on this form, I've done some nice mods to my stock 99 already:

- 62mm bored out throttle body, cleaned and painted
- new IAC switch and cleaned out all others
- removed, steam cleaned and painted intake manifold
- 4 port Bosch injectors - cleaned and painted fuel rail
- installed fuel pressure gauge
- new APN exhaust header and full exhaust system from Dynomax/Walker.
- new Feltpro manifold gasket

I was wondering if an ignition mod/upgrade is worth doing. I am running Champion plugs, standard Bosch cap and rotor and wires. Original stock coil.

Is it worth putting in an MSD/Accel/Screaming Demon coil with brass distributor and new wires?

I love modding my 4.0, but doing mods that make sense and help performance. If tossing money at this system is pissing in the wind, then I won't bother.

Thanks.

JR.

BTW.... thanks for all the great info... Tarkus is running great and a lot happier that I own it.

XJwonders

Best upgrade for the ignition system is getting the cap with brass terminals and good quality wires along with champion plugs, but if yours is a 00-01, NGK plugs work best.

STUD IN THE MUD

+1 also get the copper plugs, i have an 01 and i like the champion plugs. Just my opinion.

offroadordnance

You have OBD2, if the ignition were misfiring it would throw a code. You are good to go with what you got.

Bustedback

A higher output coil can be beneficial for igniting the crap E10 gas we're forced to run. When your XJ was built it was not designed to run E10 and the coil only need to run at 18kv to ignite the fuel at idle. Now the coil has to put out almost 40kv to ignite today's fuel at idle, that is pretty close to what the stock coil can put out at a load.

cruiser54

Leave it alone?

Bustedback

I agree, but a simple bolt on coil would be as far as I would go for an ignition system upgrade.

XJlimitedx99

If it's time for an upgrade then it's worth getting some quality parts, but I wouldn't throw money at it if you don't need to.

I ordered an ignition upgrade kit from kolak@aol.com a few days ago.

$210 for:
-magnecore wires
-usa made brass cap and rotor
-msd ignition coil with plug adapter
-auto lite platinum plugs

I asked why platinum and Nick told me that because you can gap to 0.05" with this kit they last longer.

I'm going to gap mine to about 0.045" and see how the platinums do. I'm sure they'll work just fine.

cruiser54

Not me. High failure rate on most aftermarket coils on our Jeeps.

jhc7399

Did the exact same thing with Kolak on my rebuild two months ago. Gapped the plugs at .035 on initial start up and for the first month. Went back a week ago and took them up to .050 and everything seems to be running good so far. Didn't notice any difference in the way it ran .035 vs .050.

Fred/N0AZZ

Too be quite truthful none of these are going to give you a "performance" increase as such. Some of them (4 hole injectors) may give you a smoother idle and off idle take off, but a real HP increase no not in bang for the buck.


You have a 99 so a lot of the most often done ones to older models are on yours already. Real performance would be gained on yours with a lift, bumperies, recovery points, skids, rebuild front end, better steering, tires/wheels, lockers, gears, winch that type of thing.


I have done most of them but only consider them as "Upgrades" from stock.

drhoward1988

These 4.0s dot respond well to simple bolt on mods. To gain any significant power you must either add forced induction or change engine internals such as a turbo or built stroker motor.

JamromXJ

Thanks for the opinions. I'm going to go with the brass cap and better wires just for higher reliabilty. The rest did seem over the top as I can't imagine getting more pep out of this motor than I have already. Saves lots of $$.

ehall

High quality spark wires (Accel 8mm or better) will make a difference. The rest of it is stock parts with a performance sticker on top. About the only other thing you can do is to modify the CPS to advance the timing.

cruiser54

Yep.

I like the Taylor wires. I checked a set of equal length ones as used on a chevy big block and there wasn't 10 ohms difference in resistance between them.

As for some others, they weren't even in spec!! Right outta da box. Took 2 sets to make one.