Cylinder Misfire Issues-the solution for you MAY be here

[JmP6889928]

I have posted this information in the "What did you do to your 4th gen Legacy today? thread as well.

 

I'm going to post this information in a separate thread as well as in here in hopes that it will help some of the people that are having cylinder misfire issues.

 

To add to my post above (sorry for being long winded but after I keep reading all of the "cylinder misfire" issues that keep popping up, it makes me wonder if, in a lot of cases, the issue lies here) I forgot to mention that the same holds true with dielectric grease on various electrical plugs and ESPECIALLY on spark plugs.

 

It's very easy to become overzealous with dielectric grease on spark plug boots. Because they fit very snugly on the plug and cause a seal against outside elements, even more than a film can cause the plug boot to be hydraulically pushed back off of the porcelain area of the spark plug, which immediately disconnects the plug from the clip and causes driveability issues. In some cases, it only pushes the boot back a little bit and the spark can jump across the gap and the engine still runs smoothly but under strain, it exhibits a misfire and in a lot of cases, people change the plugs, add a bunch more dielectric grease to the boots, have the same issue again, and can't figure out the problem.

 

On LGT, we don't actually have the plug WIRE/BOOT issue but we can easily do the same thing with the coil packs. Too much grease inside of the coil pack boot can cause it to hydraulically separate the coil pack clip from the plug, even slightly, and then find that you have cylinder misfire codes at the least, and at the worst strip out the bolt holes that hold the coils in place. I also absolutely recommend the use of dielectric on the coil harness plugs too, but in a VERY tiny amount. Just a smear across the female pins is plenty. When you plug your harness into the coil pack, it will force the grease down into the female receptacle and coat the metal parts and that ALL you need.

 

The best way to use dielectric grease is VERY sparingly. For some reason, many people believe that dielectric grease is there to help carry the current through the connection. This is absolutely NOT true. Common sense tells you that if the grease carried current, what would happen when you put dielectric grease on a 60 pin connector? It would immediately short all of the pins together and that would NOT be any fun at all-the magic smoke would come out of the computer and it wouldn't work any more (computers are just empty metal boxes filled with magic smoke and once the smoke comes out of the box, they don't work anymore...) and that gets EXPENSIVE.

 

NEVER use anti seize on ANY electrical connection as anti seize DOES carry current due to the metal flakes suspended in the grease. The ONLY exception is if you are in a VERY wet climate, such as marine applications, you can use anti seize on the battery terminal connections AT the battery ONLY as it will help protect against salt water corrosion.

 

Hope this will help everyone with misfire issues.

[SBT]

Great information and something you wouldn't normally think about or check. Thanks for posting this.

[ehsnils]

Personally I avoid any type of lube on high voltage items because it attracts dirt that in turn leads to incorrect current paths.

 

Keep the high voltage items as clean as possible.

[SBT]

What about silicone grease - not so much as a coating for the connection, but more as a sealant against outside dirt, water, etc., for the actual coil pack sleeve? Or would that promote moisture, and therefore corrosion inside the sleeve?

[ehsnils]

Hard call, but I prefer to keep high voltage items dry and clean. Anything that is sticky attracts dirt and then the insulating capability is gone. High voltages are also tricky to say the least to work with - things tend to get weird from time to time.

 

Another "fun" thing is that even though a material is insulating it can have a certain dielectric strength that for higher voltages acts as a short circuit. E.g. WD-40 can be guilty of this, I know that from my own experience where I had to clean ignition parts thoroughly to get an engine working again. Any contaminant that is attracted to a material like a grease or oil will also impact the dielectric strength. Aging/oxidation of a grease or oil is also a factor and when it's warm it tends to accelerate.

 

So that's why I avoid having any kind of "lubrication" on high voltage parts and rather keep them clean and dry.

 

Of course - even clean parts do attract dirt, but it takes a bit more time for it to stick.