So im driving a 2000 mazda protege since someone hit my old car and a po171 code keeps coming on and off. Ive looked up possible causes but im curious if since its going on and off if that narrows it down or not? Brother said to replace o2 sensor which can be a factor but so can other things; vacuum leaks, maf sensor etc. Any help much appreciated

 

Hi most likely intake manifold gasket is leaking. I just changed mine out good luck

 

I have one or two theories.

​​​​​​The O2 sensor measures the amount of oxygen in the exhaust gases and helps the engine control module (ECM) adjust the air-fuel mixture. An aging or malfunctioning O2 sensor can certainly cause a P0171 code. Also Vacuum leaks can introduce unmetered air into the engine, leading to a lean condition. Check for any damaged or disconnected vacuum hoses or gaskets.