My 16 3.5 eco with 151K ..
tracking down a loss of torque..dealer suggesting #1 coil shorting.
Ive never had engine lights. What can a computer at the dealer read that would indicate a short?

Because of their suggestion I am thinking of spending the $375 on 6 new Motorcraft coils. Plugs are 5K old. I could look at gap though.

I get mixed reviews on.. if considering a coil pack is a wear item at 150K- what do you think?
My theory is.. if the dealer claims they can find 1 bad coil.. whats to say 5 others aren't bad even though I have no light and can't do any swapping to test. Unless there is a testing option..or is $375 a good price to pay to know my ignition system is all new.

 

Never ever replace all coils because one might be bad.

Are you doing the work yourself?
Swap two coil positions and have codes rescanned -if the code relates to the cylinder the #1 coil is not located at, then you have exactly one bad coil (note, most people never have a bad coil, ever).
If the code stays with the same cylinder (#1 in this case), then time to dig deeper.

I don't know how a mechanic can say "a coil is shorting". Unless they can prove the coil itself is damaged internally, shorting seems like an odd description.

Unless you happened to get a bad plug, or you attempted to gap them 5,000 miles ago, the plug gap aint a problem.
Did you replace boots? If not, the boot may be leaking, caushing arc to jump which could be what they are trying to say. At which case, since I think $7 on a boot and see if it fixes the problem.
I'll send you a $300 invoice/bill if your $7 boot fixes it.

 

I only have a basic scanner. It only reads hard true codes, typically when the CEL is on. So prior to the dealer and after, it still has no codes. I'm just going off of the dealer saying shorting. They would have replaced that ignition coil (for $185) but I declined.

I did purchase 6 Motorcraft boots/springs. Those never been replaced.

I will install those and see how things are. i will certainly hold off on new coils. I just felt like what they said was misleading. Whatever they "saw" wanted to think its shorting. Idk

 

A coil is not really a wear item- it’s either good or it’s not. You can replace one but replacing all at once is not needed.

If it’s not mis-firing, then it’s probably not the coil. You did not say that it’s running rough, just “loss of torque”.

The absence of a check engine light seems odd as well.

I don’t know much, but it something isn’t adding up.

 

Coils:
A coil can develop shorted turns in the winding that reduces the spark output voltage available under lean fuel mixture conditions where higher voltage must be available or misfire results. Note; this type short will not be low resistance to the point of blowing a fuse or destroying a PCM coil driver. It involves a reduction of magnetic field that is what produces the spark at the time voltage is removed from the coil winding by the PCM driver..
These type coil faults are not detectable by a meter test of the coil winding.
They are detected by the PCM and stored in mode 6, test 83 history that does not set any code.
An offending coil can seem to work ok under normal richer conditions until conditions change requiring more reserve coil voltage such as a call for power.
The PCM never misses a misfire because it is detected by the Crank sensor measuring rotation time from the point of sparking. If the rotation time is to slow, that is detected as a misfire by comparing to the normalized average of all the cylinders as stored in a reference table.
A misfire has to occur a certain number of times as set in program, before a code is set and CEL lit..
Also the problem can be low fuel pressure or other intake/mechanical issues at 150k miles..
Good luck.

 

The camshaft position sensor is used to detect misfires.

 

No, that is not correct.
Camshaft does not measure time.
Camshaft provides a reference for fuel injection valve timing.

 

Actually, both are used. The PCM can't tell what stroke the crank is on from the crank sensor alone, it needs the signal from the cam sensor also.