Melted valves... Two valve heads were sitting on top of the piston melted and disfigured.. These were Supertech valves as well. Motor is an EJ207 with EJ20K heads.

I am pretty sure my o2 is on its way out, reads 0.06v when cold and 0.00v when driving some times..

Anyways... I was trying to diagnose a misfire at 2500~300 and yeah i was planning to buy an o2 sensor that weekend and this just happened...pics tell the story I guess. i am heart broken.

It was appox 2500~3000rpm, light throttle, cruising..2nd or 3rd gear.

Would others agree a faulty o2 sensor the most likely cause? The car is tuned using powerfc.

This thread had the exact same thing happen!

Car died and will not turn on. - Page 3 - Subaru Impreza WRX STI Forums: IWSTI.com

I need some expert feedback

uuk faulty valves? was it the intake or exhaust valves that failed? looks like it is maybe running far too much boost or too lean

a faulty 02 sensor won't cause that

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Its had some hard det going on.

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Who tuned the car?

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The one perkent...

207 with EJ20k heads. Were the pistons standard 207?
I recall Doug saying that that combo has too high a compression ratio and will ping like a bitch. Perhaps this is the results?

2.1 manley stroker pistons.

I can say i suspect the car was tuned with a faulty o2..

regarding EJ207 and Ej20K heads, i am using the correct headgasket as per the compression matrix floating around. I would like Dougs feedback.. i know they do this combo in the US.

I've heard the motor ping once and that was a on a very hot day, many months before.

Knock doesn't exceed 50, boost doesn't go pass 1.5 bar, mostly running 1.3~1.4.

i suspect the motor was leaning out, surely the o2 isnt to blame??

No, its not.

You are either out of fuel flow/pressure or incorrect mapping.

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Timing belt didnt break?

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no timing belt didn't break, it was 12 teeth off after the motor stalled..

That information in post one would of helped - Russ is on the right path with it.

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