Bosch +4 plugs - 40K mile post mortem...

Well I finally started having serious doubts about my plugs as my tour seemed to be running like cr@p above about 4500 rpm. The Bosch +4s were in for about 40K miles but seemed to be going downhill fast.

All the plugs looked about the same:

Dont know if you can see it from this picture, but a few things to note:
- The center electode is about gone

- The gap with the 'missing' electorde has grown to over .060
- The color is a sort of tanish gray, pretty normal I guess...

Conclusion: These plugs seem to run pretty smooth when new, but don't hold up as well as the OEM double platinum plugs. As other have found and posted, The OEM double plat plugs that cost less will run better over a longer plug life.

I have same plugs in mine. I will have to look at them. The very thin center electrode must have some deficiences in capacity due to the small size and wear faster. I have had experience with the original Bosch Plats with center insulator cracked and broken in some cases.
My worst experence with plugs like the plus 4s was when I had a Mazda rotary and used Lucus plugs that had a similar config (4 ground electrodes). The combination used up plugs in 5000 miles.

Anyone have experience with the NGK Iridium plugs?

yup, I have the laser welded premium ones....perfect for
first 2,000 kms ( not miles) now they miss at idle and
low rpms but are fine at high rpms or wot...

It isn't the thickness of the center electrode, it's the polarity of our spark system. On one bank the spark goes from center to ground, on the other, the spark travels from ground to center. The reversed polarity causes the metal to be lost.

Double plats are the best way to go.

Another satisfied customer of the +4's. Chris has been telling people how bad they are on cars with ignition systems like our, but no one wants to listen to him. finally some picture proof of what happens to these plugs that "last 100,000 miles." -Nick

Oh I see. We are expected to rotate our spark plugs as well as our tires. Thank you Ford for the ignition system innovation.

Its actually a very good system for getting better fuel burn. If you use the wrong parts (ie. Bosch +4's) then you will have the problems with them. Use the correct plugs (ie. double platnium) then it will be fine, and there will be no need to rotate your plugs. Would you put diesel fuel into your car, and then complain when it wont run right?

Originally posted by dellowm:
Oh I see. We are expected to rotate our spark plugs as well as our tires. Thank you Ford for the ignition system innovation.

yeah i don't understand why you are bashing a very good ignition system,when its the pos plugs,and not the ignition system in question here..it is great if you use some good double plats...

Originally posted by dellowm:
Oh I see. We are expected to rotate our spark plugs as well as our tires. Thank you Ford for the ignition system innovation.

My 88 Chevy Berreta had this system as do most GM's nowadays.
Many Motorcycles do this do. It's not new and not exclusive to Ford.

Good system with the right plugs.