1999 Toyota Avalon Multiple Misfire

1999 TOYOTA AVALON
80,000 MILES • 6 CYL • FWD • AUTOMATIC
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R_WEST_05
  • MEMBER
  • 1 POST
I scanned the car and it showed bank 1 lean and multiple misfire 3 and 4. I changed the plugs, coil pack, and both o2 sensors. The car is still showing the same codes and is still missing. Any ideas?
Dec 3, 2009 at 1:09 PM
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RASMATAZ
  • AUTOMOTIVE REPAIR CONTRIBUTOR
  • 75,992 POSTS
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)

Misfires can be caused by worn or fouled spark plugs, a weak spark (weak coil, bad spark plug wire), loss of compression, vacuum leaks, anything that causes an unusually lean fuel mixture (lean misfire), an EGR valve that is stuck open, dirty fuel injectors, low fuel pressure, or even bad fuel.
Dec 3, 2009 at 2:23 PM
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