For a little over a month, the P0171 (System too Lean) code has been coming up. My brother has cleaned the throttle and the MAF (Mass Air Flow) sensor. It then worked fine for a few weeks, then the code came up again and the sputtering started. He took it to O'Reily Auto Parts. They had said that since the throttle had been removed, it would need to retrain itself. He then tried removing it again, and cleaned out other parts in the car.

Just the other day, my car started sputtering again in the morning. It runs fine the rest of the day. Also, when I was out of town the other day, my car sat for about 4 days with a low tank of gas. When we were traveling on the highway, my reduced power engine light came on. Once I filled up with gas it was fine. I am just trying to see what could be the problem. Do I need a new O2 sensor, a change of the manifold gasket, fuel injector cleaning? Not sure. The car is good to drive, but would like to fix this problem.

  • Do you have a scantool that can view live data? The intake manifold gasket may be bad and would correlate with the rough running/misfires when cold. When the engine is cold use a spray bottle with water and spray around the intake gasket and any hoses to look for vacuum leaks.
    – Ben
    Commented Jul 6, 2016 at 14:34

1 Answer 1


Too lean = too little fuel.

I would probably try the fuel injector cleaning (Techron or comparable product) first and see if that clears up the issue. Next try swapping the fuel filter since this is usually a pretty simple/inexpensive repair.

(Sorry, can't comment with current reputation)

  • You get more rep from answers anyways :)
    – Cullub
    Commented Jul 7, 2016 at 19:18
  • Don't forget the air and electronics side. A under reporting MAF can cause lean codes though typically they will show p0171 and p0174 on v6/v8 etc... Or a O2 sensor that has an exhaust leak before the bank 1 sensor. Or a O2S that has poor range is stuck lean etc... It's pretty important to go through a thorough diagnosis when dealing with lean or rich codes so as to avoid throwing money at a problem.
    – Ben
    Commented Jul 7, 2016 at 22:11

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