'94 sport stumble

my '94 sport 2 dr 4wd stumbles under load (going up hill) but not all the time. it feels as tho for a split second it runs out of gas. I did a full bosch tune up, inc. plat +4 plugs, new fuel filter, the works, still the same, it has 144,000 mi and runs well all other times, esp when cool. only does it at normal oper temp,then right as it happens me temp raises. help!!!!

You should check your fuel pressure with a guage, check your pressure regulator while your at it. Low fuel pressure can cause this. A lean burn is hotter then a rich burn(can even melt pistons) but your cooling system should be able to handle it. You could also check to make sure your o2 is swiching correctly and is within voltage range. Check your coolant level and the condition. (is it rusty colored, smell like fuel, have oil or white foam)

i pulled the trouble codes using kry and check light, had two codes 21, 52 both indicated the o2. changed it and it runs great! thanks