40 k on this moter runs like heck catches after 2 or 3 minutes on hiway then runs better parts store guy says code means running lean.....what do i start with here.....mike in omaha

 

DTC 172 can be caused by any leaks in the exhaust system upstream of the O2 sensor. It can also be an indication you have a vacuum leak in the intake system as well. Low fuel pressure from a bad pump, faulty fuel pressure regulator or clogged filter can also cause a lean code. Once those potential causes have been eliminated it may be time to suspect a worn out or contaminated O2 sensor.