It sounds like the timing belt has jumped a tooth and the cam timing is off. I'm not too familiar with the 3.0 but I think you can pull off the upper timing covers and verify the cam gear marks while the crank is at TDC. If it jumped timing then a new belt and tensioner are probably on your short list of things to do.

95 Montero SR
3.8 MIVEC, Advance headers, 2 1/2" exhaust, Magnaflow muffler, OME shocks & rear springs, 2" body lift, 3" tank lift, 4.90s, TRE front locker, factory rear locker, Roger Brown Rock Sliderz, 315/75r16 (35") tires, Sport big brakes