This car had multiple problems. In this particular video I will be showing you the cause of fixed lean oxygen sensor signals (both banks) and very positive STFT and LTFT numbers. I will also show you how to use fuel trim after the repair to determine if you have any other problems.

This is a Ford Expedition 5.4 with a vacuum leak causing "System Too Lean" trouble codes P0171 and P0174. In this video I will show you how to use freeze frame data and fuel trim numbers to identify a vacuum leak. Then I will be using water to locate the specific area of the vacuum leak.

This vehicle came in with a long history, a severe misfire complaint that two shops couldn’t fix, and lots of parts changing along the way.

The method of timing verification shown in this video can be used on any car.