I have a 97 gc with the 4.0 and I have a random stalling issue, loss of power and the engine stumbles under a load, ive replaced the usual cam sensor, cranj sensor, pcm, tune up, tps sensor, battery terminals, down stream 02, and catalytic converter, the most recent was the cat and it ran amazing for about 3 days, idk where to look now, im getting codes 12 and 43... never had a CEL from this issue tho? Any help would be much appreciated

 

Check the fuel pressure.

 

Fuel pressure reads at 48 lbs and drops 2psi under load

 

Try repacing the fuel pressure regulator that in that model i belelive is on the fuel pump it self and while your at it the fuel filter