1999 Honda Passport EX 4WD Stalls at Idle: P0102, P0171, P0174 Fault Codes - Diagnosis & Solutions
My daughter's 1999 Honda Passport EX with 4WD and fuel-injected 3.2L engine is experiencing intermittent stalling at idle, especially after the engine has warmed up. The issue occurs occasionally during warm-up but consistently stalls when restarting after being warm. A scan tool reveals fault codes P0102 (Manifold Absolute Pressure Sensor Range/Performance Problem), P0171 (System Too Lean Bank 1), and P0174 (System Too Rich Bank 2). I have already cleaned the Mass Airflow (MAF) sensor, which temporarily resolved the P0102 code — however, the stalling persists. I also cleaned the Idle Air Control Valve (IACV), but the problem remains unchanged. Based on forum discussions, I am now considering checking for vacuum leaks as a potential cause. Before replacing the intake manifold gaskets (which would be costly and time-consuming), I'm seeking advice on other possible root causes. The vehicle is currently unsafe to drive, so I’m operating it with my daughter using mine — I miss having my own car. Any insights or diagnostic steps before proceeding with major repairs would be greatly appreciated. Thanks, Brian
Check fuel pressure to ensure the engine is receiving proper fuel delivery. Low fuel pressure can cause lean conditions and idle instability, especially in older Honda models with fuel injection systems.