I recently had a problem with a cracked #6 spark plug on my 3vz. I have 229000 miles on it and someone mentioned that as the mileage gets higher, the #6 plug will crack ever 3k miles or so. Anyone ever heard of this? Why does this happen? Truck runs great, just replaced the starter, hoping it will keep going.
Thanks

 

Interesting. This is the first I've heard of that. Due to the restrictive design of the exhaust crossover on the 3VZE, the rear cylinders (#6,#5) endure a lot of extra strain and heat. Because of this, bent valves and blown head gaskets are common. I can see how the plugs could be effected (in extreme cases). You can relieve the side effects of the poorly designed crossover by switching to headers.

 

Well, I have never heard of this. My '89 has 450k miles on it. The only problem I had with it was a burnt valve and a timing belt idler pully. Never had problems with cracked spark plugs...

 

I thought it sounded wierd also, my uncle has the same exact truck, he developed this problem, where the #6 porcelin would crack about ever 3000 miles. At first I thought he was full of it; but recently it happened to me. I replaced the plug, and now about 3000 miles later, the engine seems to be starting to sputter; thats how if figured out it was a cracked spark plug before.....Well, I guess youve been lucky to not have this problem, or i am unlucky to get it.

 

Try a colder plug...

 

When you say cracked, are you talking about the firing end? If so, that's a sign of water which could be a blown head gasket.

 

the porcelin part of the plug, (top part not firing end)