Questions and Answers
Mercury Cougar Codes P0171 & P0174
Q. Mr. Ciulla, The following is my vehicle info:
- 1997 Mercury Cougar XR7
- 4.6 liter V-8
- Automatic transmission
- 100,000 Miles
- Fuel Injection
- No ABS brakes
- P/S - A/C - Cruise control
- Rack and pinion steering
The problem I am having is the check engine light came on so I had the codes read, they were P0171 and P0174. I have replaced the front set of O2 sensors left and right ( with Motorcraft dealer O2 sensors), had the codes cleared and the problem returned with the same codes. I have new plugs and wires, air filter and airway is clean,
I have run fuel injector cleaner through the system and the fuel filter is about two years old. The car did have some hesitation prior to changing the O2 sensors, which is now gone, she runs great, smooth and fast. There are two more O2 sensors on the output side of the catalytic converter, should I reinstall the old sensors in the front of the exhaust and put the new ones on the output side of the catalytic converter? Or is there something else I am missing?
Please Advise.
Thank you,
MarkA. Common codes, see:
