sorry i think ive posted this twice but Ok guys i got the p0300 code. It said random misfire. This is my third code in a month. One on the track full throttle and two while just simply turning on my jeep (http://www.cherokeesrt8.com/forums/showthread.php?t=39869#). I have new plugs that run colder for my current set up so i doubt its the plugs. Mechanic's in my area are suggesting its the coil packs, and that i switch out all 8 coil packs. They think that its not the plugs or cylinders due to the time span in between each misfire. They said if it where the plugs or cylinders that the code would pop back up almost immediatly after clearing. They also suggested i upgrade to MSD coil packs. What u guys think?

buy the stock coil pack couple of people had problem with the msd coil

buy the stock coil pack couple of people had problem with the msd coil

What type of problems did they have?

it was misfireing i think

it was misfireing i think

so basically the same problem im having now. Well im glade i didnt buy anything yet. :eek:

I'm sure you'll find more info on them from the LX guys FWIW.

I'm sure you'll find more info on them from the LX guys FWIW.

Yea im waiting for more opinions. The shop mechanics dont specialize in our jeeps but they know racing which is big in this area. They seem to swear by the msd coils and say it would help with my current mods even adding a few HP. If thats possible.

The MSD coils aren't worth the money on our engines.

How many step colder plugs you running and what kind?

sorry i think ive posted this twice but Ok guys i got the p0300 code. It said random misfire. This is my third code in a month. One on the track full throttle and two while just simply turning on my jeep (http://www.cherokeesrt8.com/forums/showthread.php?t=39869#). I have new plugs that run colder for my current set up so i doubt its the plugs. Mechanic's in my area are suggesting its the coil packs, and that i switch out all 8 coil packs. They think that its not the plugs or cylinders due to the time span in between each misfire. They said if it where the plugs or cylinders that the code would pop back up almost immediatly after clearing. They also suggested i upgrade to MSD coil packs. What u guys think?

Have you bothered to talk to your tuner. Did you do any datalogging? They should be fix the problem.

Have you bothered to talk to your tuner. Did you do any datalogging? They should be fix the problem.

I got a emailed tune from HHP. You really think a different tune is the problem? I have not done any datalogging yet i planned on seeing if my predator did it, so i could hook it up in the evening and run with it on.

I got a emailed tune from HHP. You really think a different tune is the problem? I have not done any datalogging yet i planned on seeing if my predator did it, so i could hook it up in the evening and run with it on.

It could very well be in the tune. If you have a laptop and the cable, you'd be much better off logging to your laptop over the predator (longer log file and more PIDs)

MSD stands for multiple spark discharge.... in theory, something that would greatly improve spark blow-out in F/I and nitrous applications.

I had them on my rig.... I think they're worth the money. The people who seem to be on the fence about them probably don't run boost, or don't even dare dabble with boost over 1BAR.

Iridiums, 2 steps colder, proper gap, MSD coil packs... problem solved. These hemi's love boost, they do not particularly like boost over 10psi without lots of help getting there. On your forged high-boost blown application you can't ignore the plugs.. the more power you run, the more boost you run, the more you will have to pay attention to your plugs. You need to be pulling your plugs EVERY time you race at the track, and probably intermittently for normal driving. You need to inspect them for signs of misfire. The misfire code isn't activated by a "misfire sensor", there is no such thing... misfires are a "guess" by the engine as to which cylinder P030# is the culprit... a misfire happens in less than a fraction of a second. It can be caused by one of three things, lack of mixture (too rich or too lean for a variety of reasons), lack of compression (you have a leaking valve, leaking head gasket, leaking rings, etc), lack of spark (spark blowout or coil doesn't fire).

Unforunately there are so many things that can cause a misfire, simply screwing around with the plugs sometimes results in chasing your tail while something else is the root of the problem. If you really want to start eliminating variables on misfires.... you need to do the following:

*Multiple leak-down tests on all your cylinders, you need to ensure all of your valve seals and rings are flawless.
*Desensitize your knock sensors; with stock tuning they are very sensitive and boosted, bulit motors with different cylinder/piston gaps can be too noisy for them; they'll start pulling timing if they're left on too high of a sensitivity. Talk to your tuner and figure this out. Yes, its dangerous to turn them off, but if you want to play with the big boys, then you're going to start breaking parts, blowing engines, finding out all of the little things that make these rigs so difficult to push past certain hp levels.
*Valve float can be a problem... spin your engine fast enough with 10+psi pushing down on the intake valves and you'll run into valve float/valve slap.... you'll lose power and throw misfire codes like nobody's business. ANOTHER top-end job will have to be done, including stronger pushrods, springs, retainers, and selecting the right 'blower cam' with the proper LSA.
*The spark plug thing as described above... learn how to read them, and carry the tools to pull them at the track... they don't take long to pull out and analyze.
*Running multiple wide-bands, or AFR/datalogging on independent cylinders is going to go a long way to diagnosing problems. This can be big money, but is the only way to ultimately diagnose cylinder misfire malfunctions.


This is why when people say... "bro, just slap a blower on your 426 and run 10's and be done with it"... it makes me cringe. They have NO IDEA.

It could very well be in the tune. If you have a laptop and the cable, you'd be much better off logging to your laptop over the predator (longer log file and more PIDs)

But one of my misfires happened before i put all my upgrades and the tune. As a matter of fact , my first misfire was bone stock a month ago. The only difference was that than it said number 8 misfire and now after all the upgrades and a couple races its saying random misfire. But still a p0300 code. so my first misfire started with the regular plugs and no tune. This is why the shop here seems to be gearing toward the coils. My fiance father has a shop with a lift so im gonna try to get it over to his shop so that i can pull all the plugs and check all the cables. I just dont wanna keep running aroumd like this and break something else :eek:

MSD stands for multiple spark discharge.... in theory, something that would greatly improve spark blow-out in F/I and nitrous applications.

I had them on my rig.... I think they're worth the money. The people who seem to be on the fence about them probably don't run boost, or don't even dare dabble with boost over 1BAR.

Iridiums, 2 steps colder, proper gap, MSD coil packs... problem solved. These hemi's love boost, they do not particularly like boost over 10psi.

Well with my V3 Vortech im pushing about 8psi i think on average at full throttle. So this is the type of boost you refer too? and thanks bro that was a good break down on Misfire and the things to consider.

Anyone else Use or ecommend MSD Coils?

Anyone else Use or ecommend MSD Coils?

http://www.cherokeesrt8.com/forums/showthread.php?t=33745&highlight=msd

I'm with Winston and I also run the MSD coils packs!

How many step colder plugs you running and what kind?

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Im running the NGK R LZTR5A-13. I pulled the plugs out last night and all seems well so i plan on switching to MSD Coils. However these current Plugs where placed by my shop because of my V3 Vortech. I dont know whta step colder these plugs are, But if i put MSD Coils should i get even colder plugs?