Have a question about the coil packs on a '93

The Shape · Oct 23, 2004

A friend of mine has been having trouble with his '93 2.3 lately. It will sometimes run great then it begins to idle rough and will sometimes die on him. Well I know this could be a number of things such as EGR or Idle Air. But while checking it out for him I decided to pull the plug wires off of the coil packs one at a time to see if maybe one cylinder wasn't firing. I strarted with the coil pack closest to the firewall. Each wire I pulled off was firing and of course made the car idle like crap when disconected. I then tried the same thing with the coil pack closest to the front bumper. I could pull all four plug wires off of it with no problem and the car still idled the same! I even unplugged the electrical connector from the coil pack with no change. So I figured he had a bad coil pack. Well this moring we decide to check it out since the car was running and idling fine this morning. I could still disconnect those wires and nothing happens. I am lost I really don't understand the whole 2 plugs per cyclinder concept or why that coil pack doesn't seem to make a difference.

freakintiger · Oct 23, 2004

Correct me if I'm wrong, but I believe the coil pack you pulled the plugs off of (that made no difference) is the one that feeds the sparkplugs that fire on the exhaust stroke. They just light off the exhaust gasses one more time for emissions sake( maybe an inconsequential amount of power is made, this ain't a dual plug per cylinder HEMI drag motor).With that in mind, the engine should be able to run without that bank of plugs firing. Hope that helps!

Touring23 · Oct 23, 2004

The second plug is worth 8-12 ft-lbs on an N/A engine. Dyno:
http://home.earthlink.net/~touring23/MyDyno040315640.jpg

Many world-class competitors use dual spark plugs:
http://home.earthlink.net/~touring23/TouringHTMLLinks.html

Hope this helps.

a351Must2 · Oct 24, 2004

freakintiger said:
Correct me if I'm wrong, but I believe the coil pack you pulled the plugs off of (that made no difference) is the one that feeds the sparkplugs that fire on the exhaust stroke. They just light off the exhaust gasses one more time for emissions sake( maybe an inconsequential amount of power is made, this ain't a dual plug per cylinder HEMI drag motor).With that in mind, the engine should be able to run without that bank of plugs firing. Hope that helps!

That misconception is still around!!

Both plugs fire at the same time for combustion ... specifically, both plugs for a hot spark for combustion and, due to the way they are wired, both plugs fire a weak spark on the exhaust stroke. The weak spark doesn't even fire until the piston is almost at the top and has already pushed out most of the exhaust gases. The improvement in efficiency and emissions is only due to both plugs firing at the same time for combustion.

As for what you noticed, being able to unplug one coil pack, is due to the inhibit signal from the computer that cause only one coil pack to fire during certain conditions.

T3AL · Oct 24, 2004

could be a bad pack, have him replace the one coil pack and see if that makes any difference.

93-2.3 · Oct 24, 2004

try the ignition module you may find excellent results. the second coil pack only fires when the computer calls for it, only one coil pack fires at idle

The Shape · Oct 24, 2004

Ended up being a bad ignition module. We swapped the one off of my '93 daily driver 2.3 and it cleared right up . All of the plugs were then firing.

freakintiger · Oct 25, 2004

a351Must2 said:
That misconception is still around!!

Both plugs fire at the same time for combustion ... specifically, both plugs for a hot spark for combustion and, due to the way they are wired, both plugs fire a weak spark on the exhaust stroke. The weak spark doesn't even fire until the piston is almost at the top and has already pushed out most of the exhaust gases. The improvement in efficiency and emissions is only due to both plugs firing at the same time for combustion.

As for what you noticed, being able to unplug one coil pack, is due to the inhibit signal from the computer that cause only one coil pack to fire during certain conditions.

Touring23 said:
The second plug is worth 8-12 ft-lbs on an N/A engine.

Thankyou for pointing out my error, always glad to learn something new about this motor of mine! Now I feel better about trying to juice every drop of power out of it(should be a kick-butt daily driver soon!) .

stangs4evr-roy · Nov 22, 2004

l swapped out my coil packs for a set of 95 v6 ones (l think thats what they are)but they work great.

shanetill254 · Nov 25, 2004

is there a way of making both coil packs fire at the safe time

Touring23 · Nov 25, 2004

That's what they do during normal running (but not at startup); the two flame fronts and less pumping losses account for the additional 8-12 ft-lbs I mentioned earlier, and that's how TheShape was able to disconnect a coil pack and it continues to run.
To be more precise, four plugs fire simultaneously: The two on the compression stroke and a pair on what's called the waste spark.

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