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Q: Keep getting code 42 on KOER test. Changed o-2 sensor. Shows always rich. on 1990 Ford Bronco

Trucks been non-op past 6 or so years. Tried inj. cleaner. Checked connectors. Generally seems to run o.k. but still sometimes gets a dirty inj. Don't have a emissions manual or breakout box. Any way to check o-2 sensor with ohm meter?
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Yeah, I thought that info was there. It's a full size Bronco with a 4.9 L 6,5 speed former Forest service vehicle with 85,000 miles.
Same injector giving the trouble every time? These engines had some connector problem at the injectors. Did you change the fuel filter? How much old gas is in the tank? Don't worry with the code just yet!
Yeah. I changed the fuel filter and the #5 fuel inj. was dumping raw fuel but then cleaned up. I changed it anyway but didn't help.
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Think you have more problems then an o2 sensor. Leaky injectors/pressure regulator. Trying to remember, Warm up engine - test the gry/lt-blu wire and ground. Idle should be 0.1-0.9v, increase engine speed voltage should increase and decrease as rpms drop. If it doesn't work as stated it's probably bad.
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