my 2.5L engine is running lean- what's happening?
A few months ago, I noticed my 1994 2.5L Jeep engine rpms dropping into the 500rpm range, and the engine seemed to stumble occasionally. Changed the plugs, cap and rotor, but no change. Air filter is in good shape. I checked the engine codes and got contradictory codes- 02 SENSOR DETECTS A LEAN CONDITION, AND 02 SENSOR DETECTS NEITHER A RICH NOR LEAN CONDITION. After replacing the 02 Sensor, lo and behold, the codes remained the same- changing the O2 CHANGED NOTHING. The engine still behaves the same, and seems to stumble and run leaner in colder temperatures, and better and smoother when it's warm. What is going on? I know there is no idle adjustment possible for this engine, so now what?