P38 gems 4.6 backfire/misfire sound

Is it possible for a valve to stick open?

Grrrrrr said:

Is it possible for a valve to stick open?

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I already suggested this as a possibility....no I didn't, I said burnt! But same outcome. It would account for the fuel exploding inside the plenum chamber... However, over fueling may also account for it, which could even point to a bad injector, but with the new info about no8.... 100psi seems a little low, unless these are low compression engines are they??

As long as they're all within 10% I don't think they can be all bad.

Update took opposite side rocker cover off to find its in two!!!

At least you know what to fix now. Result!

Wesleyb69 said:

Update took opposite side rocker cover off to find its in two!!!

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So that will explain the explosions, valve probably stuck open which is similar to a burned valve which also allows the fuel/air mix to flow back and explode.

Find what caused it to fail, i.e. was it a bent valve which had jammed, was walloped back by a piston (if it's on the wrong stroke, the valve could cause a break) or was it simply metal fatigue. If either of these, you need to fix it. Is there plenty oil getting to the rockers?

Don't want to cause headache & worry, but there's nothing worse than rebuilding it, for it to happen again

Agree with Doo you don't want to do the same job twice, there is always a cause to the problem.

Seems odd that all the comps are even. 100 is too low tbh. You'll be able to run it on paraffin.

Fergie46 said:

Seems odd that all the comps are even. 100 is too low tbh. You'll be able to run it on paraffin.

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Aye, that's been bugging me too. They should be in the region of, what, 160/180psi.

I'm thinking did the exhaust valve fail to open with the rocker being broken? It would make sense with the explosions taking place in the plenum, the compressed charge blowing back through the inlet valve. I've heard of it, just never seen it before (well, technically, I didn't "see" this one either, but thanks to your video ).

I hope you can get to the bottom of what caused it and it's a cheap fix. Welcome to the Range Rover world of stunning surprises

All running smoothly now with a second hand rocker thank you all for your advice