5VZFE spark plugs

The 3.4 V6 used by Toyota uses what is refered to as a "wasted spark" system. There are only 3 coils for the 6 cylinder engine. Each cylinders spark plug fires twice per 720 degrees of crankshaft rotation, once on the combustion stroke and once on the exhaust stroke. Was this done for emmission purposes or to save 3 coils per motor, probably both. The two firings would wear out the grounds on a single electrode plug in half the time so a dual ground electrode plug was installed. Exoctic materials such as Iridium were not avalible or they cost too much compared to a regular dual ground plug so they were not installed from the factory. Many people have installed Iridium and other "exotic" plugs with no issues where other have and had problems, personally, I think the people who had issues had other issues with the truck and thought plugs would "fix" them.

 

Probably used dual electrodes to lessen emissions?

 

I bought a set of Iridiums once and gapped them (following directions I found online... TW maybe?). Gave them to my mechanic just before he put an engine in my 03 and bolted on my supercharger. He said I destroyed the plugs. Iridiums aren't suppose to be gapped. one is suppose to get the closest gap and leave them at that is what I was told. Think I read that somewhere too. Anyone know what the best approach is for those Iridiums?

 

From http://www.denso-am.com/media/corporate-news/2018/20180315_f2_spark-plug-frequently-asked-questions/

 

Yea. I read that one needs to be careful with gapping. Thought I was. Think he put NGKs in... Wish I would have got those iridium plugs back to look at them more closely.

 

I haven't had any issues gapping mine. Pre-gapped is a joke, try to measure the gap on the Denso plugs and the gap was all over the place. Most of the time the gap was way under. That being said, I have played with different gaps and have noticed no difference in engine performance. So it's probably not 100% necessary to gap them anyways.