1996 Pontiac Sunfire Runs rich

Tiny
OTISV793
  • MEMBER
  • 1996 PONTIAC SUNFIRE
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 123,350 MILES
My sunfire runs rich all the time. Replaced the oxygen sensor MAP and fuel pressure regulator. Check engine light on for lean condition. The oxygen sensor voltage never gets above.3 volts. On occassion it will clear up and run fine for a few days and the light will go out only to come back again. This has benn an on going problem but has become much more frequent lately.
Tuesday, March 3rd, 2009 AT 4:18 PM

1 Reply

Tiny
JAMES W.
  • MECHANIC
  • 2,394 POSTS
You probably already know this, but the O2 sensor range is from.1 volts (rich) to.9 volts (lean). My first thought is: the O2 sensor is sending a rich signal (.3 volts) to the ECM but the ECM is not processing the signal correctly and still thinks the 14.1 to 1 fuel ratio it's trying to maintain is still too lean so it is adding more fuel. I'm not one to blame the computer first for all of an engine's ailments, but this time it may be the cause. You may want to have this checked out.
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Tuesday, March 3rd, 2009 AT 9:53 PM

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