97 Taurus Cylinder 2 Misfire

[Jack4161]

Getting a Service Engine Soon light sometimes steady, sometimes flashing. Engine Code P0302. Changed the plugs and wires and still getting the light. Checked the coil secondary resistance with an ohm meter and have no continuity across secondary terminals 2 and 6. This is the 3.0L OHV engine. I presume I need to replace the coil due to one bad pack. However I'm wondering why I don't get code P0356 at the same time for a misfire on cylinder 6. Should I just replace the coil and expect the problem to go away.

Thanks

[brokenantimatter]

One Coil supplies two cylinders....but one coil doesn't really supply two cylinders. Ford uses.......okay to make a 2 1/2 page document short the coil pack on your engine contains two seperate ruhmkorff coils.

So your coil pack could be discharging only one coil. The coil pack is a know issues but I would first check the for dirt and check the emissions and vaccum lines.

[shorod]

According to the Ford Service manual:
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The ignition coil (12029) is mounted on the rear of the LH cylinder head (6049). The ignition coil contains three separate ignition coils. Each ignition coil is controlled by the powertrain control module (PCM) (12A650) through three coil leads. Each ignition coil activates two spark plugs (12405) simultaneously:

l one spark plug on the compression stroke. This spark plug uses the majority of the ignition coil's stored energy.

l one spark plug on the exhaust stroke. This spark plug will use very little of the ignition coil's stored energy.

These two spark plugs are connected in series, so the firing voltage of one spark plug will be negative with respect to ground, and the other spark plug will be positive with respect to ground.
-----------------
Pretty much any car on the road today uses the Ruhmkorff induction coil principal, but according to Ford, there are only three coils and each coil fires two plugs simulataneously.

An engine misfire can be caused by fuel issues as well, not just spark. You may have a faulty fuel injector as well, or a burnt valve, or low compression on cylinder #2, etc. Any of these could lead to a P0302 code.

-Rod

[brokenantimatter]

Originally Posted by shorod

according to Ford, there are only three coils and each coil fires two plugs simulataneously.

.....damnit....i'll buy a coil pack and cut it open.

[shorod]

Originally Posted by brokenantimatter

.....damnit....i'll buy a coil pack and cut it open.

Well, there will be two coils of wire in the coil pack, the primary (12Vdc side) and the secondary (high voltage side).

-Rod

[Jack4161]

Thanks for the help. Once you told me about the positive and negative voltages I realized it worked like my old Mitsubishi Eclipse. Each of the 3 coils in the pack has a primary and secondary winding and each secondary at the proper time fires each end (positive and negative) at the same time. Thus there has to be continuity or at least similiar resistance in each secondary winding. Terminals 1 and 5....terminals 2 and 6 and terminals 3 and 4. Miss on cylinder 2 was likely due to the coil for cylinders 2 and 6 starting to breakdown and likely I would have had a misfire on cylinder 6 very soon. I replaced the coil pack and all is normal now . Thanks

[shorod]

Great, glad we could be of help, and thank you for posting what it took to fix your concern!

-Rod

[brokenantimatter]

I got a hold of a use coil pack and cut into it today.

Two coils
large capacitor (not marked, to lazy to test)
copper contact plate
pcb board

[shorod]

When you say two coils, do you mean a primary coil winding and a secondary, or two secondaries (for three coils total)? Is it really two secondaries, or one that has a center tap?

What is the capacitor connected to?

-Rod

[brokenantimatter]

[shorod]

Any chance you would be able to send me some photos of the guts of the coil? You've got my curiosity up. In your diagram above, are the circles to represent coils of wire? Are there any components on the circuit board, or is it just a place to terminate wires? I would expect that the negative from the circuit board is somehow tied to the common of the two secondaries (basically a center tap) to give a reference ground for the two plugs since one will be positive and one negative.

-Rod

[brokenantimatter]

Originally Posted by shorod

Any chance you would be able to send me some photos of the guts of the coil? You've got my curiosity up. In your diagram above, are the circles to represent coils of wire? Are there any components on the circuit board, or is it just a place to terminate wires? I would expect that the negative from the circuit board is somehow tied to the common of the two secondaries (basically a center tap) to give a reference ground for the two plugs since one will be positive and one negative.

-Rod

My daughter has the camera right now (new baby) but yeah give me a couple of days and i'll email you the pictures.

[shorod]

I just sent you a Private Message with my e-mail address.

-Rod