I recently chaged my spark plugs and wires on my 1997 Fi50 4.6l 145000 miles. The center electrode was worn .020 moer on the left bank than yhey were on the right bank. I had Autolite plugs in the engine from the last time I changed them. I used Motorcraft plugs and wires this time. Any one have any idea What happened to cause this? The gaps were .056 on one side and .075 on the otherside.

 

I hear that in Australia it's the opposite

 

Did you do the change before last? Did you have the same plugs in one side as the other. Parts guys will sometimes had you two boxes of four and not realize that they are different. The fact that you gapped the old plugs tells me that you prob. gapped the new ones. you might have one side a little leaner and running hotter( increasing wear) Havne't seen it that dramatic before but I guess in theroy it could happen.

 

Yes I replaced the plugs the last time. It was about two years ago. I believe all plugs were the same but can not be sure. It seems no one else has had this problem but me. The truck is also a 5 speed manual 4x4. I drive it daily and the power was good up until the plugs wires were replaced.

 

One bank fires electrode to ground while the other bank fires ground to electrode. The oem plugs are 2 different part numbers. I believe one p/n has platinum electrode while the other p/n has plat ground. Check your owners manual. My 99 is very explicit that if you pull the plugs for inspection then reuse them that you must put them back in the same cylinder. So if you replace the plugs with new you should use double plats. If you use single plats, half will wear faster than the other 4 plugs.

There is an intresting thread on this from a year or 2 ago. I think it was also said that each plug fires on every up stroke rather than just the compression stroke. But hlf of the firings are at reduced voltage.

You can view the thread by searching for spark plug curiosity.