O2 sensor not in closed loop
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Freshman User
Joined: Feb 2003
Posts: 43
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O2 sensor not in closed loop
Have 88 f350 4wd 3.50 with 460 been trying to figure out why such poor gass milage. Have check all sensors had to replace act. but o2 will start at 0 and as heated go to about .5 volts. but will not swing. So is the O2 sensor bad? or is something else causing the O2 not to go into closed loop?
Hate to spend 38.00 if it won't fix this problem.
Thanks
Hate to spend 38.00 if it won't fix this problem.
Thanks
Laughing Gas
Joined: Jul 2001
Posts: 849
Likes: 14
From: Fayetteville, NC
O2 sensor not in closed loop
The O2 sensor should jump between 400mv and 800mv. If it stays the higher end it's running lean (if memory serves me correctly). If the reading reads around 450 or less at a constant then it's running too rich. If the engine is in deed not running lean or rich then the O2 sensor(s) are at fault.
Senior User
Joined: Jun 2002
Posts: 263
Likes: 1
From: British Columbia
O2 sensor not in closed loop
Here is how it goes, the higher the voltage, the richer the mixture. The lower the voltge the leaner the mixture. When a vehicle is in closed loop it should swing from .1 to .8 or .9 V about once every second.
To test an O2 sensor you need either a real fast dvom or a lab scope. Get the sensor hot by revving the engine at 2500RPM for a minute or so, then goose the throttle hard. The reading should be above .9 volts. If it is less than .9V replace it.
To test an O2 sensor you need either a real fast dvom or a lab scope. Get the sensor hot by revving the engine at 2500RPM for a minute or so, then goose the throttle hard. The reading should be above .9 volts. If it is less than .9V replace it.
