1UZ with a miss

[ivan129]

I'll try and make this a short story. I have a 1UZ (about 300kms or road use and possibly many more hours of garage idling) running an after market ECU. Engine developed a miss at idle and exhibit a miss when revved up so we found that it needed more fuel and inturn started fouling plugs. Checking the manifold vacuum we spotted a fluctuating vacuum signal. Did a compression test and found No7 with no comp. Lifted the valve cover and found that the very back exhaust valve was stuck wide open. Unfortunately could loosen the valve so the head came off. Found that the valve was seized in the guide by carbon. Now this is a brand rebuilt engine with 80lb lextreme springs. New stem seals, valve job and all lubed during assy. Has anyone got any clues as to how this might have occured or experienced something similar?

 

[ash]

Did they put new valve guides in?
I've seen valves seize for not enough clearance.
Also, the assembly fluid/ medium ...does it look like its burn and turned into carbon jamming material?

Got any pictures?

 

[ivan129]

Carbon build up on valve stem

Hi Ash, Clearance is not the issue, the guides were reemed prior to fitting and seem to have good clearance. It seems to look like the lubricant has been burnt and formed carbon on the valve stem. I've fixed No7 and now contempating whether I should pull out the other valves..

Did they put new valve guides in?
I've seen valves seize for not enough clearance.
Also, the assembly fluid/ medium ...does it look like its burn and turned into carbon jamming material?

Got any pictures?

 

[XR8tt]

Big chance it's a tight clearance .. It's generated heat and built up carbon in quick time.. The valve clearance could get tighter at lift if clearance was checked where
there's more wear on valve stem if used valves..
Which is why valve ceased open ...