I agree you guys are on the right track, thought I'd throw in a method from yesteryear that works pretty good with spark problems.

Open the hood on a rainy night (moisture helps) and start the engine. Turn out any lights around and look at the engine in the dark - more times than not if you have spark grounding you will be able to spot it immediately.

 

That is a great idea and would certainly be valid if it was a wire problem, but you won't see anything on an arcing coil pack boot because it's buried in the valve cover spark plug tube.

 

Possibly true, but you might be surprised. I have been before. Either way, easy first step in the process of elimination, which is really what troubleshooting is all about.

 

To diag a cracked head, which is fairly common at least here in cali, is pressure testing the cooling system and we have a boroscope we can run down into the spark plug hole to see the coolant dripping out of the crack. sometimes also a block test will reveal it as well

 

What are the conditions you're seeing these cracked heads occur?
High miles? After an overheat? Hot months of the year? Injector going bad?

 

Just age. They crack right between the valve thru to the water jacket. There isn't very much room between the valves, 1/8 in maybe so it's possible thats why they do it. The 3RZ 4 cyls actually seem to do it more than the 5VZ. My other 97 had over 200K on it without a problem so its a random thing I guess

 

I'm surprised the 5VZ is cracking heads because I don't think I've seen one yet. I've seen plenty of cracked valves and I have seen cracked heads on the 3RZ for sure too. There isn't much clearance between the two, you're right but that would definately be a serious design flaw if there were any significant number failing in this manner.

Here's a pic from my HG job:

 

Thats true. I'm sure alot do occur from overheating, even slightly and lack of maintenance. At least they don't have the H/G issue the 3.0 has. lol Overall I think the 5VZ is a great motor. I guess any eng is gonna have its issues

 

SOL!!!

I just dont understand! I changed my plugs and I thought the runner was cured (no more cel). A couple days later the same illness made a strong come back. From a periodic stutter to a persistent stutter mainly in the lower to mid RPM's. I threw the same CEL (misfire in cylinder1). So I ordered an OEM million $ coil pack and a set of ngk wires.

Installed it then disconnected the battery and CRAP same problema! I switched the coil pack to all 3 cylinders and all start ups & idle were all equivalent. Shaking/stuttering. I checked all the new plugs and they all seemed fine.

I did not throw a code yet but the way its running im sure I will.

Any Suggestions? This is my daily commuter...Im so Hurt!

 

probably your injector. you should have confirmed it was/wasnt your coil pack by moving over to the next cylinder and seeing if the miss followed the coil before ordering that expensive thing. throwing parts at a problem is an expensive way to try and fix a problem with no diagnosis. Bite the bullet and take it to a shop to have it diagnosed

 

Awww Man! I wasnt thinking right. All the other post said that they either changed their plugs, wires, or coil pack. In my case I jumped the gun and did all three. Why did the runner run great for 48 hours when I changed my plugs out?

Im in san Diego and my mecahnic is up in Carson (115 miles) would be ok to drive the runner up there under these conditions?

 

Yah I notice alot of people on here throw all sorts of parts at their cars to fix engine misses and problems of the sort instead of doing an actual diagnosis and saving money and frustration. With these injectors, they will sometimes be intermittant. they will work ok one minute and then crap out on you the next. I wouldnt advise you to drive that far with a engine missing. You may need to bite the bullut and go to the dealer. *YUK* See if you can find a reputable shop who specializes in toyotas

 

I agree it sounds like an injector at this point.

Here's how you test them:
https://www.yotatech.com/forums/f2/9.../#post50418688

This is for #5 so your #1 would be at the very front of the motor on the passenger side. If you find out that the injector is bad, you should consider eventually getting all new injectors because it seems like often when it rains, it pours so to speak (ie at higher mileage they start going bad in rapid succession). The other option would be to eventually get a low mileage used set off of ebay.

 

Cool...looks like I have to tow it up there... I will keep you all updated. thanks so much from the bottom of my heart!