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P0171 Fault in 1997 Dakota 5.2L V8 with Automatic Transmission - Intake or Vacuum Leak Diagnosis?

Model: 1997 Dakota Fault Code: P0171 Posted: 2007-07-24 19:50

I recently started experiencing engine jerking and a significant drop in fuel mileage after several hours of towing my trailer. This only occurs during extended use, and I've noticed the appearance of fault code P0171 (Rich Fuel Mix - Bank 1). The vehicle has accumulated over 150,000 miles but remains in excellent overall condition. In addition to the fuel issue, I’ve observed that the A/C airflow occasionally shifts from the dash to defrost while cruise control is active. When I disable cruise, the air returns to the dash position—this behavior strongly suggests a vacuum leak, though I have not yet identified the source. Importantly, no other diagnostic codes are triggered. I’m wondering if these symptoms are related and what could be causing them. Given that this issue only occurs under heavy load or prolonged use, is it likely due to an intake system failure or a vacuum leak? Any insights would be greatly appreciated.

Related fault codes
P0171
Comments (8)
Anonymous 2007-07-25 07:21

A blown intake gasket could be the culprit—worth checking first.

Anonymous 2007-07-26 19:49

It seems like there's limited discussion on this issue. Is anyone else experiencing a similar P0171 problem with their 1997 Dakota?

Anonymous 2007-07-27 05:54

I have a Ram truck with the same 5.2L V8 engine and it exhibits identical symptoms—any thoughts on what might be causing this? Could it be related to intake or vacuum components?

Anonymous 2007-07-27 06:41

Inspect all intake manifold gaskets and vacuum hoses for signs of leaks—especially around the intake manifold and throttle body.

Anonymous 2007-07-27 07:36

I strongly believe this is either an intake or vacuum leak. Just want to confirm if there’s anything else I might be overlooking.

Anonymous 2007-07-27 07:42

The plenum pan gasket beneath the intake manifold may have failed—this is a known failure point in 1997-2000 Dakota 5.2L engines. A blown gasket can cause improper airflow, leading to P0171 and symptoms like engine pinging or oil burning. There are TSBs and updated replacement parts (now steel instead of paper) available—be sure to check those for repair guidance.

Anonymous 2007-07-27 17:02

Thanks to all the input—I’m planning to remove the intake manifold to inspect the plenum pan gasket. This seems like a solid next step.

Anonymous 2007-07-28 06:28

Please keep us updated on your findings—this could help others with similar issues.