Codes

Hi I have codes P1151, P0300, P0174
Causing the vehicle to fail emissions. 98 expedition 4.6

Do all the codes need to be cleared and anyone else have any direction to start with troubleshooting these codes?

P0300 is lean bank misfire. P0 174 is system too lean. P1151 is a heated oxygen sensor trying to correct for an overly lean condition. The overly lean condition could be caused by leaking contaminated fuel injectors, Leaking fuel pressure regulator, or Low fuel pressure.
Induction problems. Air leaks after the MAF. Vacuum leaks, PCV system, improperly seated engine oil dipstick. Stuck EGR valve,
Base engine--OIl overfilled, cam timing off, cylinder compression.
Exhaust leaks before H02 sensor.

Check the vacuum line on the back of the intake manifold. These are known for this line aging and splitting creating a severe vacuum leak and causing the codes especially the PO174

Do a Google ''Youtube Auto smoke test''
This test will find your unmetered air leaks on your Intake, EGR + PCV systems.
Watch the bad vacuum video.