I have a 1995 Mustang with a 1998 3.8 ltr V-6 engine. The check engine light is on so I went an purchased a OBD reader because it seems like I always have a check enging light on one of my 4 vehicles. The reader says "bank 1 lean, bank 2 lean" I can not figure out why the car is running lean. I car seems a little sluggish with snapping the throttle and it runs rough when you give it high rpm. The car always stalls once or twice in the morning. I hooked up a timing light just for the sake of seeing what the timing mark was doing and it was all over the place. I used a Snap-On timing light that had timing advance knob on the back and it made no difference on timing mark position. This engine has the coil pcak and not distributor so I dont know what to do about that. I have put a new fuel filter and no change. I have about 25 to 30 lbs of fuel pressure. I have hooked up a vacuum gauge to the vacuum port that feeds the break booster and it says "good engine"... I have added a K&N filter after this problem has started. Can some one give me a few things to check? I am not interested in anything more then stock performance. Thanks!
the front oxygen sensors are bad. Also get some MAF cleaner and clean out the sensor element a dirty one will cause a lean condition also. But if it said bank 1 and 2 than both oxygen sensors are bad.
I will see if this happens. I cleaned the Mass Air Flow Sensor and the problem went away for a short time. Now I have bank 1 running lean after about two weeks of running with no check engine light.
Before you start changing parts because people say it IS this or that, take a look at all of your sensor readings and find out what is outside parameters.
Had this problem in my 95 3.8. I went through everything and finally changed my MAF sensor. The problem went away and hasn't returned.
As far as the timing light and timing marks not moving when you turn the knob, the problem should be in the light. The knob doesn't actually change the engine timing, it just lets you align the marks so you can figure over-all timing.
I have seen the internal EGR ports plugged with carbon ,usally all but one, causeing all your EGR to go thru that cly. This cause it to read lean on one bank....... Pull your upper plenum clean all 6 ports ..... should cure problems .......
1998 3.8 ltr runs lean 
