boraxman

My trucks 3.4 engine tends to crack sparkplugs regularly, about every 4k miles.

When I say crack, I mean it is actually putting a barely visable tiny crack on the porcelin by where the electrode extends out. This crack is enough to make the cylinder misfire and throw the misfire code, generally run like crap. The plugs always look fine with the exception of the crack thing. This has happened 7 or 8 times already. My guess is I may have a lean condition going on or something.

My engine has a 165k on it it and for the most part runs great. I use Denso dual electrode plugs, but it has happened with other types. I have replaced my coil paks, wires, vacuum hoses, all plugs, pvc..etc.

Anyone know whats happening here or experience the same?

I posted this on a different forum also, just looking for some different opinions...thanks!

Andrey

are you using the proper torque when replacing your spark plugs?

MTL_4runner

That sounds like a leanout to me.
Get that fixed ASAP!!!

boraxman

Yes, the cracks are happening where the tip of the electrode comes out, you can kind of see on the pic.

boraxman

How? Its not throwing any codes??

MTL_4runner

Huh?



Does this only happen just with one or two cylinders or does it happen randomly across all 6 cylinders?

boraxman

so far 3 different cylinders, it does give the cylinder misfire code when the plug goes bad, but thats all.

mt_goat

Maybe a dirty fuel filter is dropping fuel pressure enough to run lean?

MTL_4runner

Are they all on the same bank (side)?

Also, do you gap your plugs or do you install them right out of the box?
If you do gap them, please explain your method.

Can you please post a clearer photo of the plug you took out, I can't see anything on the previous one you posted.
Zoom out alot if you have to.

boraxman

Both sides. I only use dual electrode plugs. I dont gap them, but do a visual to make sure they all look the same.

MTL_4runner

You said 3 cylinders are consistently problematic, which ones are they? #1? #4?

Maj

Any detonation problems? Older motors can get carbon build-up thus raising the compression ratio and causing detonation problems. Is timing to spec?

boraxman

3, 6 and 4 cylinders so both sides of motor. No detonation at all, not sure about the timing, but usally running perfect. I dont believe its my driving habits as I never rap it out, mostly 3000rpm between shifts. I do always run regular gas, maybe I should switch grades? I did the fuel filter about 50k ago. If you open the pic you should see the crack.

icerunner

Hey,
Have you tested the compression of each cylinder?
Also what brand of gas do you run? and is it "TOP TEIR" FUEL or plain jane discount stuff (btw, there is no "right or wrong" here i'm just curious)
Also, just curious what type of oil?

Also consider running "Shell V power" or "amoco ultimate" for a while as the higher octane will stop some of the pre-detnotaion and the added cleaner will help clean up the valves and injectors. Run at least 5 Strait tankfulls of the Ultimate of "V power" and also consider running techron injector cleaner on a FULL tank of gas.. Careful the tank must be full as you will kill the crap out of you new plugs
good luck and god speed.
icerunner over and out

dallison

too much heat somewhere