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Coil On Plug Conversion

akorna

NAXJA Forum User
Anybody tried converting from the distributor to coil on plug ignition on the 2000 and later XJ's? Might be as easy as a computer & coil hardware swap for a 96 or later OBDII vehicle.
 
You would need at least the entire wiring harness, computer, coil packs, cam sensor and probably alot more. Why bother?
 
FrankNBrew said:
You would need at least the entire wiring harness, computer, coil packs, cam sensor and probably alot more.? Why bother
I understand that combined with the redesigned exaust, or a headder,and intake manafold its worth about 5hp. not to mention its supose to be more reliable, and water reasistent. Though i maybe wrong.
 
The coil on plug ignition uses a cam sensor that sends a signal to the PCM. The PCM then fires three coil packs one at a time. There is one coil for two plugs, and the coil fires both plugs at the same time, because of this there is spark on the power and exhaust stroke. This design is simpler because of less moving parts, and less wear items (spark plug wires, cap, rotor). It may be less sensitive to water.

Here is why this design sucks. Because of the three coils, if you plan on using an aftermarket ignition, you have to use a controller that is a lot more expensive (an MSD DIS vs. 6A). There are no high performance coils made for this system, and if the coil rail goes bad, it is a lot more expensive than the single coil used by the conventional ignition.

The later model PCMs that use the coil on plug ignition also control the transmission. That might cause some problems. It also has more emission controls (that is why they added the intake to keep the HP the same).

If you look at it from a $/Hp standpoint, it would be an expensive upgrade. You would see much bigger and cheaper Hp gains by putting an aftermarket ignition controller on your stock system. Then you can have multiple spark, and a rev-limiter.
 
Not having worked on one or played with any yet they look like a PIA to do plugs on, seems like it would be at least as much work as changing injectors by the time you get all the parts off. I may be wrong, it may be simple to work on but not having done any I can't say with any certainty. Maybe some owners who have done plugs and stuff on them can chime in.
 
Plugs arent bad. Three or Four bolts hold the rail on and it pops right off as a whole unit. lay it out of the way and pull the plugs like any other cherokee... pop it back on when done. all the bolts drop through the top of the rail so they are easy to get to.

Jay
 
FrankNBrew said:
You would need at least the entire wiring harness, computer, coil packs, cam sensor and probably alot more. Why bother?
AMEN!! I swapped in a 98 comp into 97 to accomodate the ax15 (XJ had aw4 before). This cause whole sorts of headaches: your comp might expect sensors that you don't have thus resulting a check engine light, if you swap the harnesses also expect that you might have to swap sensors out cause plugs dont fit (or splice the wires)..... ANyways, it's definately possible but it'd be a major PITA.
 
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