Question

Codes p0171 and p0174 on my 2000 Ford Econoline Van 8 Cyl. What's the problem?

Answer 1

P0171 Fuel trim system lean (bank1)

P0174 Fuel trim system lean (bank2)

Bank 1 and bank 2 thats the left and right cylinders, means you are taking maor air than fuel. Probable causes are MAF (mass air flow) under reporting due to contamination,a simple MAF cleaning may help this, Vacuum leaks getting past the MAF this can come from ruptured PCV hoses, or the PCV valve itself, vacuum leaks are the main cause of this code,Low fuel pressure, can causes this ,due to fuel filter.

Answer 2

P0171 FORD - Fuel Injection System Too Lean Bank 1
Read more: https://www.autocodes.com/p0171_ford.html

P0174 FORD - Fuel Injection System Too Lean Bank 2
Read more: https://www.autocodes.com/p0174_ford.html