97 running rich, lean error code

[opa1604]

I'm working on a 1997 jeep grand cherokee that is getting horrible gass milage, running way to rich(determined by reading the plugs, but the CEL is throwing a p0171 code. I have changed the wire set, distributor cap and rotor, and installed correctly gaped plugs, which i believe to be the original problem. When i pulled the O2 sensors, both upstream and down were covered in about 1/4 inch of soot. I think the problem is clogged O2 sensers are telling the engine it's not getting enough fuel and it keep dumping it in causing the engine to run rich but think it's running lean. Does this sound correct? And any possible other problems that i can check. thanks.

[corning_d3]

That sounds like the culprit to me, but it may not be the whole problem. It could have a leaking injector or something. Test the fuel pressure with the key on, engine off. It should be around 44-54 psi for both the 4.0 liter, and the 5.2 V-8. If the pressure bleeds down quickly after the key is shut off, there could be an injector not closing properly.

[opa1604]

I'll try to check that also, I ran some solvent through the injectors, but i also know that if there severly fouled that may not be sufficent to clean them.the owner replaced the o2 sensors a few months ago, but didn't fix the problem that caused the failure in the first place. Luckily the o2 sensors are still under warranty and i talked to the parts store and they agreed to replace them.