[LX5liter]

Do a compression test first. If you have little or no compression on 1 or more cylinders you might have the valves adjusted too tight, ( not enough shims ). If its low on all the cylinders then I would suspect your timing sprockets are out of sync, ( valves opening and closing at the wrong times and possible valve to piston clearance issues ). If you have good compression across the board then your timing is probably way off, or the rockers may be over shimmed and not opening enough.

Just my $.02. I hope it helps.