How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask roybelding Your Own Question
roybelding, ASE Certified Technician
Category: Mercury
Satisfied Customers: 5718
Experience:  35 years of retail operations on all vehicles
Type Your Mercury Question Here...
roybelding is online now
A new question is answered every 9 seconds

Mercury Mountaineer 4x4: P0171P0300P0301P0304I'm fairly

Customer Question

I'm fairly sure I've had 0301 and 0304 before just not together, replace plug works fine for a while, if I remember right the plugs don't look burned or anything, fairly sure I replaced all O2 sensors, is there something I am missing, I've tried replacing the coil pack but the plug was the fix every time, is there something else I could check?
Submitted: 2 years ago.
Category: Mercury
Expert:  roybelding replied 2 years ago.
good morning my name is ***** ***** I will assist
the 171 is a lean code for bank 1 or the passenger side of the motor. it is set when the long term tims are too high, not because the O2 sensor is bad. it could be a vacuum leak along that side of the motor, pcv system, mass air flow sensor or low fuel pressure.
the 301, 304 codes are miss fire codes. usually plugs, wires or coil. if you have not done, I would replace the coil. you said you tired but did you actually replace it???
the 300 is set whn more than 1 cylinder has set a code for missfire. the common denominator here is fuel pressure. low fuel pressure will cause the miss fire codes as well as the 171 or lean code. I would rent a tester from a parts store and see if the fuel pressure is exactly correct.