System Too Lean (Bank 1) Symptoms include stalling at idle, rough idle, poor MPG, loss of power, high pitch sucking sound from the engine bay. This is typically caused by a vacuum leak. The most common cause is a hole in the elbow at the PCV valve. It may be hard to see so you'll want to pull it out to check it. Also look at the elbow that connects the PCV hose to the intake manifold. It can get a hole there as well. This is 90% caused by a vacuum leak and not the O2 sensor. Most people (ignorant ones) will just say it is the sensor because it set the code. That code is a good sensor reporting a lean condition. Just replacing the sensor without checking for other problems first would be like replacing an entire wire harness when a light goes out instead of checking the bulb and fuse first. Other causes can be a bad sensor, bad MAF, low fuel pressure, or an exhaust leak. To fix the elbows on the PCV valve you can pick up new ones from the HELP section of the local part store. The part numbers for the elbows from the Help section are:
47028
47029
The one that goes on the intake manifold fits the nipple on the manifold snugly. But, it doesn't fit snug on the line so you'll need to use a clamp on that part. The one on the PCV valve is a very tight fit at both ends. If you don't want to bother trying to rig this up, you can purchase a new line from Ford. The part number is: F8CZ-6853-CA.
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trouble code P0171
trouble code P0171
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