Check Engine light, again. 2003 Mazda 6s, 151k miles, single owner. A couple weeks ago, my check engine light came on, code was read as P0174. Per the lookup, the definition is “Lean air/fuel ration bank 2” and this means one of four things:
Low fuel pressure, “large vacuum leak”, dirty/defective MAF sensor, or “engine mechanical condition”. There was no change to how the car was responding to the gas pedal. According to the auto parts guy, the only one of those that would not effect the responsiveness is a dirty MAF sensor, so I got a can of cleaner and used it.
Not only did the check engine light fail to clear, a second code has now popped, P0171. Per the lookup, this one’s definition is “fuel trim bank one condition” with four items to check:
“If bank one and two codes set together suspect fuel pressure or MAF sensor”, Oxygen sensor defective, ignition misfire-repair, fuel injector problem.
There is still no noticeable change in responsiveness to the gas pedal, but now there is an intermittent roughness at idle, and sometimes on start up it’ll idle at ~1.2k RPM instead of the normal 500~700. Googling around indicated I should check my fuel consumption and it is within my expected range.
Since I just cleaned the MAF, it’s not dirty, and engine response is still good so my ill-informed logic (ie, I could be completely wrong) tells me that it’s not low fuel pressure. Obviously, the MAF could have died and I have no real way to determine that without replacing it. Google searching also says these two codes together could indicate a vacuum leak. If there was a vacuum leak, would there be any noticeable symptoms?
I am, for all intents and purposes, flat broke. I’m trying to determine if this is something I can attempt to fix myself with no real mechanics tools and no way to lift the car to get under the engine or if it’s outside my scope, try to narrow it down before bringing it to the shop.