Originally Posted by xjgary
As a side note I found another Jeep owner with the same problem at this Cherokee forum http://www.cherokeeforum.com/f2/gas-oil-36065/
Makes me feel a little less crazy
I have a suspicion this might be a more common issue that goes undiscovered until the engine spins a bearing or dies for some mysterious reason.
I wonder if it has something to do with how much fuel is in your fuel tank? Is it possible for excess fuel to get drawn into your vacuum canister then that fuel gets sucked into the engine?
If not then the only way fuel can get into the base, if you can eliminate tampering, is through the injectors. The ECM provides ground to close the circuit to pulse the injectors. I wonder if the pulse rate is being increased? That gives you the extra fuel but doesn't necessarily mess with performance.
If you have an exhaust leak anywhere before the O2 sensor that would cause the O2 sensor to send a false lean code to the ECM and increase the time the injectors pulse, dumping unneeded extra fuel into the cylinders.
I do not remember but what condition are your injectors? Maybe their internals are gummed up or just tired and can't close completely.
Make sure you are running the correct spark plug gapped properly. It has often been reported that the high tech spark plugs often do not work well in these engines. Autolite or Champion plugs seem to perform just fine.