My newly acquired 2001 with 130k miles was running perfectly, so I decided to mess with it anyway. I replaced the NGK iridium single ground plugs with NGK Platinum dual ground plugs. Now I have a stumble at idle below 1000rpm. I confirmed the gap with a wire gap gauge. I replaced the wires with NGK a few weeks ago and it was fine. I thought maybe too much dielectric grease, so I cleaned everything with no change. Wires are routed correctly. Suggestions?

Coils are not making or possibility starting to fail. You can find the testing procedure in my signature for the v6.

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Thanks. I re-installed the old plugs and it runs fine again. I'll try new coils with the new plugs.

wait a min... Where did you buy these ngk iridium's from? If eBay or amazon I am guessing you got some counterfeits. :-(

Dielectric means NON conducting. It's an insulator to keep the fire from going where it shouldn't. You should put it inside the boot but not on the connector or the metal tip of the plug. You can put it on the ceramic portion of the plug to help removal.

I made that mistake a long time ago on some NGK plugs and got the same result as you; misfiring plugs. I cleaned the plugs and connectors with something (maybe alcohol) and reconnected. It fired up and ran fine. Clean all of the metal on the plug and wire connector where you put the grease.

It's fine if you want to use it for something like coating your battery terminals, but not putting it on the terminals before you make the connection. Even so, it would still jump that very small gap. On a high energy ignition like a spark plug it will block it.

On the actual connections. its best to use conductive grease. I personally, put nothing on my spark plugs connections and have no issues. :-)


"Dielectric means NON conducting" yes it best to be on the outside of a circuit not in the connector itself. Sort of put on after the circuit is together to keep the water out.. :-)

Did you replace your wires too? Were any damaged prior to installation?

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The coil boots also wear out eventually. If there is discoloration on the boot end then time to replace just the boots.

The plugs came from Rock Auto. The only variable here is the plugs. New plugs misfire and old plugs don't. One of the new plugs did not discolor like the rest in the short time it ran. I'm guessing that one wasn't always firing. I'm thinking I may have gotten some copper anti-seize or something on the tip. Of course it was the last one I changed back, so I'll have to re-install the new ones again. As for the grease, I would've thought high voltage would be more likely to jump the gap, not less. Like when you get zapped by static before you touch the door knob. Or when a plug wire has a bad spot and the voltage jumps to a nearby ground.

Spark plug voltage is very high, amperage is low (but high enough to give you a good zap). Static electricity, like when you shuffle across a floor or just walk across a room is also high voltage, low amperage. Bottom line is not to put anything on your spark plug connections. They should be clean and dry. Anything you put on those contact points is going to reduce the voltage sent to the plug and you don't want that. The boot will keep the contacts clean.

I’m also thinking you got knockoff NGK plugs.

You can call NGK and they can tell you if they are real plugs or fake ones based on the numbers they ask for from the plugs.


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Well... I cleaned off the excess dielectric grease and the anti-seize that had gotten on the tip of one plug. Re-installed the new plugs and no problems. Basically I got complacent doing something I've done a thousand times before. Thanks for all the help and tips. I learned something new about dielectric grease in the process.

Excellent news. Glad it's fixed

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