PO171/PO174 Fault Code Fix for 2001 Ford F150 4.2L Engine - Intake Manifold Bolt Grommets Required

After experiencing the PO171 and PO174 fault codes on my 2001 Ford F15-0 4.2L engine, I replaced the intake manifold O-rings on the lower plastic section. While shopping for parts at a Ford dealership in St. Louis, several mechanics advised me to replace the intake manifold bolts with grommets or seals—this is a known issue that can trigger these codes. This detail was not mentioned in many online posts, so I want to emphasize: do not skip this step to save money. The effort and potential for recurring problems make it worth investing in proper components. Specifically, the top rear intake cover bolts are especially prone to failure. After completing the repair and replacing all relevant parts—including the grommets—I have successfully cleared both fault codes. Thanks to everyone who contributes to this forum—your insights save me time and frustration! Roach