4 Wheel Drive/SUVs: 1998 jeep Grand Cherokee Laredo, jeep grand cherokee laredo, jeep grand cherokee

Question
I have a 1998 Grand Cherokee ZJ  4 .0L Straight engine not a V6 or V8. It has done  150,171 miles.The problem that i am experiencing is that the engine is Misfiring when idle  and it has been consuming too much fuel and it is giving out smoke on it exhaust. The Diagnose scanner read  Code P0171 system too lean. please tell me what to is wrong and what part or parts to change
VIN 1J4GZ58S1WC269097
Thanks


Answer
Ralph, it sounds like it could be alot of different problems, it could be the o2 sensor , or sensors, fuel pump, fuel pressure regulator , injector, I really dont know what to tell you to put on to fix it check the fuel pressure , and tell me what you have . ADAM