Gen 2 Head gasket failure? Photos included

I don't think those plugs are the cause of your problems, you may want to stick with those plugs until you get to the bottom of what may be causing the issues. Don't throw money into a non issue....the plugs and PVC valve will not improve your current situation

 

Agreed

 

Looking at the photo of the spark plug, the electrode gap seems to be different. I don't know the correct gap, but generally the electrode gap of the 4 spark plugs should be the same, maybe 1.2mm? It can be corrected with a feeler gauge. I would like to ask, has anyone used spark plugs with dual platinum contacts, is it helpful to mpg?

 

You probably would not want to go to dual platinum, as that would be a step down from the OEM plug, where the center electrode is iridium.

For a Gen 2 (this is the Gen 2 forum), the Toyota-specified plug is SK16R11, which has a 0.7 mm iridium center electrode and a platinum tip on the ground electrode. So everyone with a stock Gen 2 already has better plugs than what you are asking about.

For a Gen 3 (your profile mentions a 2010), the Toyota-specified plug is SC16HR11 (in earlier documents SC20HR11). This has a longer reach but the same electrode types and dimensions. Same for Prius v.

The Gen 4 Prius and Prius Prime use FC16HR-C9, and all years of Prius c use FK16R-A8. The F plugs are needle-to-needle types: the center electrode is a 0.55 mm iridium needle, pointed at a 0.7 mm diameter platinum needle on the ground electrode. Those will be pretty hard plugs to beat.

Denso's aftermarket "Iridium TT" flagship only differs from those by making the center electrode skinnier, 0.4 mm instead of 0.55. That will mean just a slightly lower voltage needed to fire them, and just a slightly shorter life.

The ECM has some pretty sensitive measurements to show you how your current plugs are doing. For starters, there are the misfire counts, accessible by viewing the misfire monitor. If those are staying at 0 for all cylinders, your current plugs are getting the job done. But beyond that, there is a metric called the misfire margin (at least starting in Gen 3; I don't know if Gen 2 tracked this). This number can be negative (misfires are happening) or positive (if less than 30, at risk for misfiring; higher than 30, not really at risk, higher is better). Last time I checked mine it was something like 134.

If you have looked at your misfire margin and it is some very comfortably high number like that, the odds are pretty much nil that any change to any kind of better plug is going to change anything. The plugs only do one thing and a high misfire margin shows they're already doing it better than they need to. (That doesn't mean, given that we're human, you couldn't change to fancy plugs and convince yourself you feel wonderful things happening.)

If your current misfire margin is lower, getting down near 30 or worse, then it is possible a change of plugs could improve something. But it would also be worth investigating whether anything else is going on with the engine that could be contributing to the low margin.

 

Does your Prius consume oil?

And how much?

I believe it's possible for some carbon/oil to seep through the spark plug from underneath during combustion from the pressure overtime as my Prius appeared to have done the same thing when it consumed oil.

There was blackish carbon residue on the Ignition coil side of the plugs but no oil in the actual spark plug holes or oil seeping from the valve cover gasket.

My Prius was a severe oil burner, burning a quart of oil every 1,000-2,000 miles since about 100k miles. The cylinder that had the worst oil consumption had the most oily residue on the spark plug.

The spark plug was literally soaked in oil on the combustion side as was the actual piston and it seemed to carry over to the coil side of the plug.

You can do a Berryman B-12 Piston Soak Procedure to attempt to cure the oil burning.

It cured my oil consumption.

My Prius still consumes Pennzoil Platinum though.

Here is what my old spark plugs looked like:



The one on the left was the chamber with the worst oil consumption by far as evidenced by how wet the piston and spark plug was with oil when observing with an endoscope camera.

But there was no evidence of oil leaking from the valve cover in any chamber. No wetness on the sides of the spark plug holes or pool of oil at all.

Also, headgasket replacement will not fix this. Start with a B-12 Piston Soak to cure your oil consumption, then see what happens.

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Also notice how there's nothing on the nut part of the spark plug? Only the inside white part? And how the color/consistency matches where the crush washers are?



Combustion pressure appears to be forcing oil vapor/carbon up through the center of the spark plug.

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I don't know how to read the misfire coefficient, so I posted the misfire detection results for different time periods, during which the engine may stop sometimes.

 

I think your original post of "rougher starts/stops" is a subjective thing. So that may or may not be a problem. As for burning 1/3qt every 1000 miles, it's perfectly normal for engines to use oil. It only gets alarming when the oil burning gets to 1 qt every 600 miles or so.

So you have to decide if you have an issue or you don't have an issue. Maybe drive it for 5000 miles before you can make that determination.

Plugs are not very expensive, if you feel you want to throw $60 bucks at new plugs, then go for it and see if your "rougher starts/stops" will get better.

 

Denso reported that some counterfeit plugs were poorly-enough made that bits of the electrode or ceramic could break and fall into the cylinder, which would not be good news.

Sure, it's in Denso's interest to say that, but ... if I thought I had counterfeit plugs in there, I'd probably change 'em.

 

Here is the cause of your discolored spark plugs.

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