2005 Nissan Altima "2002 jeep limited 6 cyl" Questions

2002 jeep grand cherokee, oil pressure guage to the maximum high limit. Oil level okay, Oil change mechanic says common among these cars. I'm still curious what to do. thank you. 6 cyl. It may be that

2002 jeep liberty limited? 3.7L v6... need a whole new engine the 6th cylinder isnt firing in my 02 liberty.. need a whole new engine. cant seem to find a reasonable priced engine for a 2002 liberty..

2002 4.7 jeep grand cherokee limited. It has a miss. Smokes but no code. White smoke. Oil looks perfect on dipstick. No bubbles in coolant at radiator. Water in the gasoline, or a leaking head gasket.