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Thought I'd celebrate and put in new plugs, wires and coil pack.

chuckj5

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My 1996 Explorer just rolled over 200.000 miles, replaced plugs, wires and coil pack with DENSO parts. Before the new parts there was no check engine light, truck ran OK, quick start, not a lot of power, now it is showing PO 351 and PO 353. Bought Motorcraft wires, coil and plugs and replaced the Denso I had installed. Still shows same codes.. Swapped PCM, same codes. Kicked bumper, same codes. Checked wiring sequence to coil left-123, right 465.
Any clues to what may be wrong. I like my Explorer, should I take it to a dealer for a $1.000,00 checkup?
 



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Fix4Dirt

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any issues with the wiring up to the coil pack? and did you clear the CEL?
 






J_C

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Are you 120% sure you got all the wires on the right plugs and coil terminals?
 












Fix4Dirt

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only other thing i can think about would be both are bad? highly unlikely though... still got the original pack? maybe try clearing CEL (disconnect battery for 10(?) mins or clear w scanner) and drive for a bit to see if it come back... if it comes back, then reclear codes and try putting the old pack in... thats the only other thing i can think of, as that one was 100% proven to have worked prior to swap
 






donalds

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Did the original coil pack check out ?
I'd swap that back in and see
The coil is grounded using its mounting bolts so clean them
 






Mbrooks420

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Can you swap coils left to right and see if if changes banks?
 






J_C

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I'm not seeing any ground on the ignition coils (on the wiring diagram) except when the PCM does it through the "IGN Coil" wires. See attached PDF.

Pictured below is an item of potential interest. At the risk of being annoying by asking about mixing up wires again, did you notice that on the ignition coil module, that the 4/6/5 side is out of order?

Also notice the pins, IGN Start/Run should always have 12V (with ignition in run position), then PCM grounds each in sequence with the engine running. Using a multimeter, you should get the same resistance (on the unplugged coil pack itself) reading between the 12V power lead pin and CD1, as you get between 12V pin and CD2, and 12V pin and CD3. If any of those read open circuit instead of *similar* resistance, the coil is bad. I know it seems unlikely since you replaced the coils.


Probing the plug to the coil pack (while plugged in, engine running) it should read near 12V on each respective CD1, CD2, and CD3 pin, until the PCM momentarily grounds it to complete the circuit for each cylinder spark. If it never gets momentarily pulled down below 12V to fire the spark plug, would seem like PCM is bad yet you replaced that too, so I begin to wonder about bad wiring or one of the two bulk connectors as mentioned here:


On the attached wiring diagram, the coil wire that's tan/Lt-Green, also goes to the PCM but they routed it the long way, goes to PCM pin # 78. All else fails, use a multimeter to check resistance between each respective CD1, CD2, and CD2 connector contact, and the respective pin on the PCM connector... but they go through one of the bulk connectors in the topic linked above so that is another place to look for a bad connection as already mentioned.

There are more wiring diagrams linked in my sig below, but the only one I thought relevant (besides mentioning PCM pin #78 is where the tan/lt-green wire from the coil pack goes) is attached.

Ignition Coil Pack Diagram.png
 

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  • engine-controls-1-of-4-2.pdf
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donalds

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Last time I looked the coils are grounded
Here

Ignition Coil Pack Diagram_kindlephoto-142453022.png

I'm most likely wrong
Helped me with a idle problem
 






J_C

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^ It would not surprise me if that is a chassis ground, but only to a sort of faraday cage assembly (internal metal plate) to decrease EMI, not to make the coils themselves function. I suppose in theory, it might be possible that the magnetic field in one coil, could induce a charge in an adjacent coil if the structure isn't grounded, but that doesn't seem like it would prevent the coil from functioning, would manifest itself more at higher RPM (? Just guessing on that).

It can't be a ground for the coils themselves because it's an always live 12V going to them, has to have the PCM make and break ground to fire the plugs.
 






Mbrooks420

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They are chassis ground as Donalds stated.
 






J_C

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To clarify, the coil pack does not need bolted on or grounded through the bolts at all for the bare minimum function of running. That will serve as a % of heatsinking, which is good, but that is long term lifespan related, and as far as EMI shunting to ground, better AM radio reception related, not make or break functionality to run the engine.
 






C420sailor

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I seem to remember a recent post where a guy installed a new coil pack for ***** and grins and his truck ran like shi* and threw codes.

Try the original pack
 






c96drumm

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I guess everyone here but me has all the codes memorized. I don't and I won't look them up. You should say what they are in your post.
 






Fix4Dirt

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I guess everyone here but me has all the codes memorized. I don't and I won't look them up. You should say what they are in your post.

po351=problem with coil running cyl1 or the circuit behind it, commonly said as "ignition coil A primary/secondary corcuit malfunction"

po353=problem with coil running cyl3 and circuit/plugs etc with that, commonly said as "ignition coil c primary/secondary circuit malfuntion"

i think... 😀
 






c96drumm

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po351=problem with coil running cyl1 or the circuit behind it, commonly said as "ignition coil A primary/secondary corcuit malfunction"

po353=problem with coil running cyl3 and circuit/plugs etc with that, commonly said as "ignition coil c primary/secondary circuit malfuntion"

i think... 😀
Thanks!
Wish I had something to offer that isn't already covered. Hope the OP finds the problem and shares the solution!
 






fast_dave

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@chuckj5

I read that you have a '96

IIRC, from experience, the early build factory coils had a different numbering set-up on 2 of the cylinders.

Did you keep the old coil - next to each nipple it's corresponding cylinder is stamped in black ink (on the beige colored glue).

This is from experience/memory 16+ years ago , so ultimately it would help to reference the old coil (if you still have it)

HTH -
 






410Fortune

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The coil pack numbering does not matter

The firing order for 4.0 ohv is
852650d.jpg




Ignore the numbers on the actual coil pack if they do not match this diagram

Many people forget that the front cyl on pass side is 4 not 6

I know you said it’s covered because you numbered the wires etc but it is good practice to check firing order one wire at time against the correct chart
 






fast_dave

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^^^ Just sayin' - No codes or check engine lights before the OP touched it.

Free advice - for what's it's worth - your mileage may vary :)
 



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410Fortune

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I work on these trucks daily and have for 20+ years, yet I still have these charts taped up on the shop wall
 






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