my car runs a th idle BAD.

Question

I havE 2001Ford Focus its a4 cylinder.I've replaced the o2 sensor front and The back.I have a P0171 code. I also cleaned the MAF Sensor. Still the problem persists? Any Ideas?I have 170000 miles on it. Runs great except at idle.

Answer 1

Hi there,

Usually on this particular engine you get this code with a rough idle when the vacuum hose for the PCV valve is cracked or soft and sucking closed when the engine is running.