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P0171 and P0174 Fault Codes on 1997 Ford F250 4x4 7.5L 460ci - Vacuum Leak Diagnosis

Model: 1997 Ford F250 4x4 7.5l 460 ci Fault Code: P0171 Posted: 2012-08-25 19:33

This is the second time I've encountered DTCs P0171 and P0174 on my 1997 Ford F250 4x4 with a 7.5L 460ci engine. The first instance occurred about two years ago when Ford replaced the PCV valve and hose. Could this be due to wear or failure of these components again? This issue reappeared approximately one month after a DPFE replacement that cleared the MIL light. I'm seeking advice on possible root causes, especially in relation to vacuum system integrity and fuel delivery. Any insights would be greatly appreciated.

Related fault codes

P0171P0174

Comments (3)

Anonymous 2012-08-26 09:23

Inspect the PCV hose elbow located at the bottom rear of the throttle body for cracks, disconnections, or deterioration. Also check for other vacuum leaks in the intake system. Verify fuel pressure to ensure it's within manufacturer specifications.

Anonymous 2012-09-10 23:22

Mohawkmtrs wrote: Inspect the PCV hose elbow located at the bottom rear of the throttle body for cracks, disconnections, or deterioration. Also check for other vacuum leaks in the intake system. Verify fuel pressure to ensure it's within manufacturer specifications. The issue was a vacuum leak. After Ford replaced the DPFE several months ago, they installed hoses similar to fuel lines—stiff and not designed for vacuum applications. The hose had a sharp bend over two inches, which caused poor sealing on the DPFE. I replaced the fuel line with proper vacuum hose and now have no DTCs. Thanks, David

Anonymous 2012-09-11 07:00

Glad you found the solution—this is a common issue with older Ford F250 models when using non-vacuum-rated hoses after DPFE replacements.