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2003 Mercedes Benz SL500 Code PO171 and PO174

Tiny
RNHOLMES
  • MEMBER
  • 2003 MERCEDES BENZ SL500
  • V8
  • 2WD
  • AUTOMATIC
  • 69,000 MILES
I can't seem to find a list of possible items that create system too lean Any ideas on what to look for starting with most likely. I cant hear any vacuum leaks It probably idles a little rougher than it should runs smooth at 1000 RPM up. Scanner says no misfires or other problems Any ideas?
Randy
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Monday, April 14th, 2008 AT 11:36 PM

1 Reply

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
P0171/P0174 check below-

A lean fuel condition can be caused by:

* Low fuel pressure due to a weak pump or leaky fuel pressure regulator. (Use a fuel pressure gauge to check fuel pressure at idle)

* Dirty fuel injectors. (Try cleaning the injectors)

* Vacuum leaks at the intake manifold, vacuum hose connections or throttle body. (Use a vacuum gauge to check for low intake vacuum)

* Leaky EGR valve. (Check operation of EGR valve)

* Leaky PCV Valve or hose. (Check valve and hose connections)

* Dirty or defective Mass Airflow Sensor (MAF). (Try cleaning the MAF sensor wires or filament with aerosol electronics cleaner. Do NOT use anything else to clean the sensor, and do not touch the sensor wires)
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Tuesday, April 15th, 2008 AT 4:50 AM

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