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Old 10-18-2014
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Coil issues

I have a 93 2.3 ranger that is only firing on half of both coils. I have tested both coils and they show the proper resistance. The ICM was just pulled and has tested ok as well. The best i can tell 2 and 3 fire on exhaust and 1 and 4 fire on intake , I'm lost anyone have any ideas?
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Old 10-19-2014
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Only the exhaust coil fires when starting engine, just FYI, once RPMs are above 500 intake coil should start working

ICM ground is often "iffy" on these, so ICM tests fine but when reinstalled it has same issues, reground locally.

OHM tests on coils can show a bad coil, but can not absolutely confirm coil is good, unfortunately.

Ford uses a Waste spark system, the Waste spark system means 1 coil in the coil pack sparks 2 spark plugs at the same time, one will be for cylinder on Power stroke, the other will be on Exhaust stroke, so Wasted.

Spark plug wires should look like this on the coils
----
3 1 (same coil)
2 4 (same coil)
----
4 2 (same coil)
1 3 (same coil)
----
Front

So 1 and 3 fire at the same time, and 2 and 4 fire at the same time

Because 1 coil sparks 2 plugs the plugs are wired in Series so one of the plugs sparks in reverse, i.e. from ground to electrode, instead of electrode to ground
Coil(+)-----Spark Plug------Spark Plug----Ground(-)
The reverse spark is slightly weaker, it still works, just weaker which can show up if there are problems with the system.

This is why the Dual Coil pack setup is wired as it is
Normal spark would be the hole closest to coil connector
So coil packs are wire so all cylinders have one spark plug getting Normal spark.

And because of the Series wiring one out of spec spark plug wire effects 2 spark plugs
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Old 10-19-2014
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Well after re-installing the ICM i started getting spark on all four plugs on the front coil. After running a ground from the bottom left bolt on the ICM to the frame i lost the spark again, now i'm back to the original issue. I'm thinking i may just have two bad coil packs. Can the ground issue be internal on the ICM? This is where i currently sit the x represents no spark.
------
3 x1
2 x4
------
4 x2 ----This coil has been intermittent on 2 and 3
1 x3
------
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Old 10-19-2014
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I would hit the wrecking yards and pick up a couple of coil packs, they used these same packs on the V8 Fords, just FYI

They run about $75-$90 new, $50 on ebay, wrecking yard is "what ever price you can get", lol, but bring OHM Meter to test, not fool proof but best to test first.


Well something is amiss if adding a ground caused problem to surface, it does mean something is wrong but can't say it is ICM or coil.
I would ground to engine, frame could be a floating ground which may be an issue, PCM(computer) is usually grounded on firewall and there is a ground strap from engine to firewall, or should be.
Frame is isolated from body and engine by rubber mounts, or should be, lol, and it should also have a ground strap from battery's ground on engine to the frame.
These ground straps are often removed during mechanical service and then never hooked back up, "hey it's all metal, so it's all a ground", but this isn't true.
4 grounds on vehicle should be:
Battery to Engine(for starter motor)
Engine to firewall(for computer and dash board)
Engine to frame(for lights and fuel)
And there should be a smaller lead on neg terminal hooked to Rad support frame(for head lights)

Last edited by RonD; 10-19-2014 at 04:14 PM.
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Old 10-19-2014
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Thanks, i'll give it a shot.
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