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Discussion Starter #1
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Got off highway doing 120 km/h slowed down to 50km/h for in town speed limit low on gas less than 1/8th tank. Car started to act strange as loss of power, acceleration . Check engine light came on and started to flash constantly. I was luckily down the road from my house as this started to happen. Pulled the codes and I am getting misfire on cylinder 1 ,misfire on multiple cylinders. Spark plugs were looking rough and the gap was not consistent between all of them ranging from .030 - .040 .Changed my spark plugs out with new NGK G power plugs gapped at .040. car will start and idle fine for 20 seconds and than putters and dies, I am smelling alot of unburnt fuel . Cleared misfire codes and started up for second time . Same results - starts perfectly 20 seconds later putters and dies . No check engine light. No new misfire codes. Battery voltage at 14.47 when running ... Put gas in with Jerry can , half can of sea foam in fuel tank other half in the crank case . Starts up, runs . Idles from 900-1000 rpm for first 10 seconds . Runs fine now at consistant idle of 550-600 rpm and up to operations temperature.. has been running with no hiccups for 10 mins. Any speculation on what may have caused the misfire ? Was it the spark plugs? They had less than 20,000 kms on them . Would being low on gas cause a misfire? I still have an unburnt fuel smell after shutting car off ( buddy of mine commented weeks ago and said it smelt like a 2stroke was under the hood)
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I would suspect the coil packs, and possibly the front O2 sensors.

If I got similar codes, I would start by replacing the coil pack feeding the cylinder 1.
 

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I would also start to suspect the ignition coil. A failing ignition coil should result in lack of spark in two cylinders. (coil 1 feeds cylinders 1/6, coil 2 feeds 5/8, coil 3 feeds 4/7 and coil 4 feeds 2/3). So if you are registering a misfire on cylinder 1, and the coil is to blame, I would bet that cylinder 6 was having a similar problem. If the problem starts to happen more often, what you could easily do is swap the 1/6 coil with another one that is working. If the codes jump to the other cylinder, you have a pretty good idea that the coil is bad. If the problem stays on the same cylinder, there are some other things that you can try. Might also try swapping the plug wires with another cylinder too.

I believe you have a 96 4.6L correct?
 

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Discussion Starter #4
Thanks guys . Ignition coils didn't even cross my mind but makes sense. Common for them to "skip a beat" every so often when they are on their way out ? Is replacing all coil packs at same time recommend or only what is needed? oxygen sensors are a good suggestion as well Would explain the bad fuel economy I have been experiencing. I have driven it since than about 20 km's and no problems have arrived . Yes 1996 4.6L gems.
 

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Yeah, when my coil packs started to die on me, I would get occasional misfires that would correct itself and run fine for awhile. Misfire frequency gradually got worse, however, in no time.

I don't know how easily accessible coil packs are on GEMS, but on a THOR it's a pain so when I went in to do the repairs, I replaced all (2 coil pack assy in THOR's case) so that I don't have to go back in there for awhile. Besides, I think coil packs are wear items so probably good practice to replace all at once.
 

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Discussion Starter #6
The coil packs are surprisingly easy to get to on the gems (my opinion). I did a part search and found atlantic British is selling the whole setup the 4 coil packs,mount with connector for $130 CDN .
Another website I use is rockauto. Cheaper ussauly but they only sell the coil packs individually ranging from $15-$45 cdn. Crazy to see that one 02 sensor is the same price as the whole coil pack kit.
I will probably order the whole kit off Atlantic British for the convenience of removing the unit as one.
either way .. shipping to Canada is always expensive no matter where i order from
 

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Yeah, when my coil packs started to die on me, I would get occasional misfires that would correct itself and run fine for awhile. Misfire frequency gradually got worse, however, in no time.

I don't know how easily accessible coil packs are on GEMS, but on a THOR it's a pain so when I went in to do the repairs, I replaced all (2 coil pack assy in THOR's case) so that I don't have to go back in there for awhile. Besides, I think coil packs are wear items so probably good practice to replace all at once.
Yea, my low on power and occasional misfire crept up slowly on me as well. I only REALLY started to notice it when I was doing some offroading and in 4L and putting the engine under a really good amount of load. Then after that, I started to get it while driving on the streets and whilest idling as well. In my case, I threw a capacitive secondary ignition probe on a scope and checked each plug for proper spark. I was then able to easily see the two cylinders that were not getting a good spark at all. If you have a cheap oscilloscope laying around, the probes to check are only like 10-15 bucks. Well worth the money in my opinion.

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Comparing it to a malfunctioning coil waveform, I saw pretty much same behavior in the waveform:
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Yup, thor coil pack replacement wasn't fun at all and like Theo, I replaced both since I was already in there. Believe GEMS is much easier. But yea, If you can spare the change, might as well replace the others as well. Then keep the old working coil packs as spares if you have any issues down the line.
 

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