Expert: Sean Halliday - 10/22/2006

Question
I'm getting the code P0171 (fuel system too lean bank 1). What does "bank 1" mean? It still runs fine but the check engine light is on. What could be causing this. Also the temp and oil press. gauges flutter sometimes.(?)
Thanks,
Keith

Answer
This is caused by possibly a leak at your intake manifold.Bank one means either the right 3 cylinders,,or the left,3,,it depends on if your 6 or 8 cylinders but i believe the explorer is a v6,i have seen this happen and the car runs fine until the piston actually goes into melt down mode ,,this is a serious fault with these cars and should be fixed at once.Sometimes it is caused be the EVAP having a leak but either way it will have to be looked at by a certified FORD mechanic.Although the engine may seem cool enough it is inside the cylinder that runs too lean and runs very hot.This causes detonation and makes the cylinder run out of control,,,the gauge flutter may be related to this.May not be the gasket and it could be the fuel pressure regulator but either way its serious.