Engine Performance problem
2004 Ford Focus 4 cyl Two Wheel Drive Automatic 35000 miles
Engine warning light turned on
Trouble code was P0171, system too lean
Garage cleaned MAF sensor & reset trouble code
Trouble code turned on again after a day
I ordered a new MAF sensor from Global automotive FL
After installing new MAF, RPM is very unstable when engine is cold and car barely accelerates
When engine warms up it's OK, still a bit chubby
Light hasn't turned on for 2 days after replacement
Hi AmitZohar, Welcome to 2carpros and TY for the donation
Other contributing factors for a P0171/P074- Lean fuel condition could be caused by one of the following below: 1. Vacuum leaks
2. EGR and PCV valve.
3. Low fuel pressure.
4. Dirty fuel injectors.
5. Mass Air Flow Sensor.
6. Oxygen Sensor.
October, 27, 2010 AT 3:12 AM
OK, but after than I replaced the MAF sensor and things got worse. Is the new MAF sensor bad? Does it point to another problem?
November, 4, 2010 AT 7:55 AM
Same thing happened to me. Turned out it was the pcv hose where it goes into the intake at the rear of the engine. Small angle hose which ford charges $50.00 for. Got mine at a scrape yard for 5 bucks.