What would cause a spark plug to wear down more

[threeputtpar]

than the other ones? I just changed the plugs in the 4.0 in the Mountaineer and 5 out of the 6 were only worn down to .056 from .054, but the one in cylinder 1 (front of the engine on the driver's side) was worn down to .072.

I change them about every 50-60k miles becasue they are easier to get out, and the ones I removed were Autoline single platinums. Replaced with Autolite coppers since we will be selling/trading the vehicle in a couple of months.

The vehicle was stumbling a bit on cold starts, as it did back just before I changed the plugs the last time, so that is why I changed them this week instead of just leaving them until we disposed of the vehicle. The stumble has gone away, but I'm curious on what would cause the one plug to have such a large gap after ~55k miles. No COP, there is a coil pack with 6 plug wires.

 

[Falken]

Running lean and hot from a vacuum leak, partially clogged injector etc would be my guess.

Do you have a check engine light? Maybe you have a misfire code from that cylinder.

 

[HerrStig]

A lean condition in that cylinder will cause the plug to wear moe quickly. Anything from a clogged injector to valve lash off can do it.

 

[Quest]

spark plug wear is primarily dependent on the temperature, the higher the temperature, the quicker the erosion.

Both Faklen and HerrStig are right RE: lean condition, but overleaning the mixture will definitely lead to throwing a code.

a non-functioning EGR would also be the cause, so is a timing/knock sensor issue.

Q.

 

[threeputtpar]

Yikes, none of those things sound all that good.

I guess I'll have to monitor it and see if the new copper plug shows anything in the next couple of months and then send it down the road.

 

[mechanicx]

Also you should use double platinums/iridiums with a wasted spark ignition, not single, for even wear.

 

[threeputtpar]

Originally Posted By: mechanicx
Also you should use double platinums/iridiums with a wasted spark ignition, not single, for even wear.


You're probably right (and the service manual reccomends them), but I went the cheap route since we replacing it in a couple of months. Just wanted to clear up the cold start issue while we drive it the rest of the summer.