Change the Coils… not always the answer

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2006Lincoln

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I’ve read some very interesting and detailed posts that covered in great detail, the most common failure of the Lincoln LS: Coils. My thread asks the question: Has anyone actually researched and tested for the root cause for these extremely common coil failures?
Most will say… just change all the coils and spark plugs together, not individually as they fail. Check for oil contamination from a leaking gasket or vacuum leaks. Some of which, are the culprit, and fix the issue. But, what if you have no oil leaks or vacuum related problems? You’ve changed all coils, spark plugs and injectors. You’ve checked ECM pulse with a noid light, resistances with a multimeter, fuel rail pressures and bleed down tests, but still experience misfire, especially when the engine reaches operating temperature?
I’ve discovered the true root cause of this issue: Engine design.
One thing that is overlooked in every thread I’ve read so far… how heat affects wiring resistance. For every 1 degree Celsius, copper wire resistance will increase 0.4% (obviously dependant on gauge). But, what gauge wiring runs to the coils/injectors on the Lincoln LS? Approximately 18ga. This smaller wire, combined with engine heat trapped under the “coil cover plate”, ultimately leads to heat-sinking and drastically increases the wires’ resistance. Thus, creating a domino effect that destroys components like the coils and injectors.
The very design of the 3.9litre coil wiring harness is at fault.
 
2006Lincoln said:
I’ve read some very interesting and detailed posts that covered in great detail, the most common failure of the Lincoln LS: Coils. My thread asks the question: Has anyone actually researched and tested for the root cause for these extremely common coil failures?
Most will say… just change all the coils and spark plugs together, not individually as they fail. Check for oil contamination from a leaking gasket or vacuum leaks. Some of which, are the culprit, and fix the issue. But, what if you have no oil leaks or vacuum related problems? You’ve changed all coils, spark plugs and injectors. You’ve checked ECM pulse with a noid light, resistances with a multimeter, fuel rail pressures and bleed down tests, but still experience misfire, especially when the engine reaches operating temperature?
I’ve discovered the true root cause of this issue: Engine design.
One thing that is overlooked in every thread I’ve read so far… how heat affects wiring resistance. For every 1 degree Celsius, copper wire resistance will increase 0.4% (obviously dependant on gauge). But, what gauge wiring runs to the coils/injectors on the Lincoln LS? Approximately 18ga. This smaller wire, combined with engine heat trapped under the “coil cover plate”, ultimately leads to heat-sinking and drastically increases the wires’ resistance. Thus, creating a domino effect that destroys components like the coils and injectors.
The very design of the 3.9litre coil wiring harness is at fault.
Click to expand...
I love this comment! Personaly i don't like just throwing parts and money at something unless i know exactly whats wrong and causing my issues, that way when i fix it im not just guessing and maybe i can come up with a way to keep it from happening again.
 
Go invest in a Fluke infra-red thermometer and point it at the exhaust manifold covers when fully warmed up. I'll find those two locations are the hottest parts in the engine bay. The manifold covers have one mica sheet sandwiched by two aluminum shells that are to shield the heat method. That heat from the manifold covers affect the engine mounts & wiring harness covers and connectors. The hydrualic engine mounts have a rubber construction & a white rubber umbrella heat shield to protect the top cone profile of the mount. The exhaust system heat is destructive to plastic and rubber parts that are near in the LS tight engine bay. Also the metal structural frame parts may distort dimensionally.
As for the coils failing due excessive heat, the coill covers hold the heat in when ran pass full engine warmup. Engine soak heat, spark plug heat through the boot & spring wire, and coil operating heat dissipation are acceptable when new. But with age that mica sheet wears and the manifolds begin over heat the engine bay. The way the manifolds over heat is by conduction & radiation. The air is heated below the valve covers plus the exhaust manifolds gaskets are stamped stainless steel units which conduct hot exhaust heat back into the cylinder head face. Heating the aluminum head throughly reaching the coils. This excessive heat first hardens the valve cover gasket material then the spark plug hole o-rings and then hardening the coil wiring sections.
As a temporary electrical coil fix due to the heat, I would use DeOxit D5 deoxidation spray on the connectors followed up with silver paste applied to the connector pins & socket, boot spring end to enhance electrical current flow.
( What are the three best conducting elements ? - Google search )
This analysis is what I found when I performed a complete exhaust system insulation job from the cyl heads face to the back of the mufflers. I can say this approach worked but helped me learn other conditions not revealed before.
If you desire what i did for the insulation job in detail I can re-post it with greater detail.
 
SteveOwens said:
Go invest in a Fluke infra-red thermometer and point it at the exhaust manifold covers when fully warmed up. I'll find those two locations are the hottest parts in the engine bay. The manifold covers have one mica sheet sandwiched by two aluminum shells that are to shield the heat method. That heat from the manifold covers affect the engine mounts & wiring harness covers and connectors. The hydrualic engine mounts have a rubber construction & a white rubber umbrella heat shield to protect the top cone profile of the mount. The exhaust system heat is destructive to plastic and rubber parts that are near in the LS tight engine bay. Also the metal structural frame parts may distort dimensionally.
As for the coils failing due excessive heat, the coill covers hold the heat in when ran pass full engine warmup. Engine soak heat, spark plug heat through the boot & spring wire, and coil operating heat dissipation are acceptable when new. But with age that mica sheet wears and the manifolds begin over heat the engine bay. The way the manifolds over heat is by conduction & radiation. The air is heated below the valve covers plus the exhaust manifolds gaskets are stamped stainless steel units which conduct hot exhaust heat back into the cylinder head face. Heating the aluminum head throughly reaching the coils. This excessive heat first hardens the valve cover gasket material then the spark plug hole o-rings and then hardening the coil wiring sections.
As a temporary electrical coil fix due to the heat, I would use DeOxit D5 deoxidation spray on the connectors followed up with silver paste applied to the connector pins & socket, boot spring end to enhance electrical current flow.
( What are the three best conducting elements ? - Google search )
This analysis is what I found when I performed a complete exhaust system insulation job from the cyl heads face to the back of the mufflers. I can say this approach worked but helped me learn other conditions not revealed before.
If you desire what i did for the insulation job in detail I can re-post it with greater detail.
Click to expand...
All that heat build-up you are talking about is the reason i put a toggle switch on the black/white wire running to my LS's fan so i can keep maximum air flowing through my engine bay at all times. I believe that running my fan at high speed and a couple of other minor things i have done is why i haven't had much trouble out of anything under my hood. The only cooling system parts i have ever had to replace was a water pump a bad thermostat and the thermostat housing piece that holds the thermostat because one of the little ears broke off. Everything else is OEM and never been replaced even the degas bottle is the one that came from the factory.
 
I'm glad you had good service from the plastic cooling parts and improvising an override fan swirch. The thermostat retaining ear can be reinforced with a countersunk 4-40 screws which seal fine with a #42 drill. As for the plastic cooling parts they're all 6061 aluminum now. When the mystery leaks start look under the engine, the middle engine leak is most likely the hot coolant feed from the from v of the block and around driver side rear fendor may be the de-gas tank.
 
I love the look of the covers over the ignition coils, but I think they trap heat causing the failures. last summer I decided to drill several 3/16" holes along the sides of the covers were they are not seen. Don't know yet if it will work, but worth the try.
 
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