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post #1 of 10 (permalink) Old 06-24-2014, 07:31 PM Thread Starter
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Sparks plugs

Well after changing to bosch iridium plugs and two hours of my day, I encountered the dreaded stalling and shuddering mentioned throughout this forum. I have sincechanged them back to champion oem plugs and no more stalling. Brilliant! Wish I had checked before going through the first change. Live and learn. Thanks to all those that posted this issue before me.

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post #2 of 10 (permalink) Old 06-25-2014, 11:27 AM
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You should stick with oem brand plugs. I run the NKG iridium1X and have no problems. The 3.7 calls for NKG. But you must use oem when dealing with the 02 sensors.


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post #3 of 10 (permalink) Old 06-25-2014, 01:35 PM
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Quote:
Originally Posted by rhobll View Post
But you must use oem when dealing with the 02 sensors.
Huh? Thats a new one on me?

I totally agree, and the Commander is NOT the only vehicle that experiences this, that there a lot people complaining about problems after switching brand or type of plugs different than OEM, even though they are suppose to be equilvalent and perfectly compatible replacements.

I have always "assumed" it was because of new ignition systems and ignition schemes the manufacturers have been using on their engines were the cause, i.e. new kinds of ignition systems or schemes are much more sensitive to the subtle differences between brands or types of plugs.

I can't imagine how O2 sensors are behind problems with different than OEM plugs? But I'm open minded, and definitely want to hear the explanation to consider if its true/plausible or NOT? I'd agree that incomplete ignition would wreak havoc with the O2 sensors, that doesn't make the reverse true that just because O2 sensors are there they create some sort of problem with ignition because of subtle differences in the plugs.



I have a partial explantion that would explain some problems, BUT NOT ALL. The wasted spark ignition scheme, which some Commanders have and lots of other vehicles as well. This scheme has 2 spark plugs share 1 coil, the plugs are in cylinders 180 out of phase, and both plugs fire at the same time, by the one ignition coil. For one cylinder, its when the spark is needed and the other cylinder is when its in the exhaust stroke, where the spark won't hurt (it can even help burn any unburnt fuel being exhuasted which improves emissions). This means the plugs fire twice as often as the old systems, so you should replace them twice as often. But the big thing to realize is how the coil fires both plugs, the plugs are actually wired in series with the coil and the ground. The coil actual pulls up current from one plug as drives down current to the other plug. What that means is current flows the opposite direction in half the plugs in the motor. That is no big deal, until you try to use platinum or irridium plugs, those plugs have harder metals that resist the errosion of the metal from the spark (the whole anode and cathode deal). But, if you reverse the current in one of those plugs, the spark now jumps from the softer steel to the harder platinum or irridium, and that causes the softer steel to errode even faster than if it was steel to steel. This is why they now have double platinum/irridium plugs, with the same metal on each electrode on the plug, so the plug can handle current flowing in either direction and last equally as long. BUT, that still shouldn't create a problem with ignition right away, and people complain about that, as soon as they switch brand or type of plugs, that should work equally well, they immediately start having ignition problems. All that I just described, means half the plugs would wear down/errode much faster than the others, you'd have problems 5k miles down the road, NOT right away.

So, I really haven't heard a good explanation why lots of modern engines have ignition problems immediately, when they switch brand or type of plug that should be equally compatible?


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post #4 of 10 (permalink) Old 06-25-2014, 02:38 PM
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Mongo, problems have been reported when using the Bosch O2 sensors.

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post #5 of 10 (permalink) Old 06-25-2014, 02:46 PM
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Quote:
Originally Posted by jeep5253 View Post
Mongo, problems have been reported when using the Bosch O2 sensors.
Ok, I think I misunderstood what rhobll was saying. So, like the spark plugs, using other than OEM O2 sensors creates problems right away?

That makes sense and I can see how that could be very true. Or, considering people are reporting problems, if I'm changing out O2 sensors, I will use OEM sensors.

I thought rhobll was saying, using other than OEM plugs can create problems, and it is because of the O2 sensors that you have to use OEM plugs, which doesn't make sense to me, but he wasn't saying that.


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post #6 of 10 (permalink) Old 06-25-2014, 04:05 PM
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I had problems with Bosch O2 sensors. I think I switched to ACDelco.

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post #7 of 10 (permalink) Old 06-25-2014, 10:36 PM
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I thought rhobll was saying, using other than OEM plugs can create problems, and it is because of the O2 sensors that you have to use OEM plugs, which doesn't make sense to me, but he wasn't saying that.[/QUOTE]

I didn't mean that...I used Bosch plugs and had issues, i.e. misfire, rough idling, etc. Went back to the original NKG brand, and upgraded to the iridium 1X, im guessing 30k ago, and have never had a problem. I read that as long as you stick with oem brand, the iridiums would work better.

When it was time to replace the 02 sensors, did the same thing, bought bosch! If I pulled out within a minute of startup, the engine would bog down and attempt to stall, but never would. If it warmed up for a couple mins, this would never happen after pulling out. I read here that the bosch had higher 'set points" or something and the oem sensors had lower opening points. I think it had to do with the heat temp.. Anyway, bought 4 from mopar.com, installed them and haven't had any issues since.

I'll be doing the annual trip to NC soon, and I'm curious what the iridium plugs look like before I do the 12 hr trip. will pull a couple soon for inspection even though the 3.7 runs smooth and quiet with great excelleration.


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post #8 of 10 (permalink) Old 06-26-2014, 01:21 PM
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Sorry for the misunderstanding, I see exactly what you mean now.
Quote:
Originally Posted by rhobll View Post
I'll be doing the annual trip to NC soon, and I'm curious what the iridium plugs look like before I do the 12 hr trip. will pull a couple soon for inspection even though the 3.7 runs smooth and quiet with great excelleration.
Now out of curousity, do you have one coil per plug, like my brothers '07 3.7L? or do you only have coils over the plugs only on the driver's side bank and ignition cables crossing over to the Passenger side bank, like my '10?

At some point they switched the 3.7L from one coil per every spark plug to a 2 plugs sharing one coil (which has to be a wasted spark system).

And NGK Iridium IX only have an irridium at the center electrode as well?

Reason I ask, what I talked about in the previous post, if you have the wasted spark system (you may NOT, but I do) that means half your plugs have the current flowing the reverse direction, so the irridium plugs with the reverse flow would probably have that steel lower electrode erode away much faster than the irridium plugs under normal current flow will have eroded away that irridium electrode.

So if you have a wasted spark system, pull a plug from under a coil and pull a plug from under a ignition cable only and compare them and their gap see if I'm right in that one of the plugs will erode much faster than the other, if they do NOT have the same metal for both electrodes.


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post #9 of 10 (permalink) Old 06-26-2014, 09:58 PM
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I have one coil per plug.... I would guess the irridium is at the center electode. but not certain. I'll post a report after I pull them. Your theory makes sense about the reverse flow...wonder why they would change the design?


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post #10 of 10 (permalink) Old 06-27-2014, 01:59 AM
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Iridium would be the center electrode. My guess your plugs are fine with a coil per every plug.

Perhaps they did it for cost savings, reduced the number of coils by half. Or, maybe emissions, going to the wasted spark help the engine pass emissions for that M/Y.


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