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Re: o2 sensor CEL, fuel economy Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Thu, 13 Jul 2006 09:31:00
In Reply to: o2 sensor CEL, fuel economy, TML   [Profile/Gallery]
, Thu, 13 Jul 2006 07:58:26
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A front O2 sensor CEL means that the signal from the front O2 sensor isn't doing what the ECU expects it to do. For a '97, it assumes that after warm-up, the O2 sensor makes so many transitions above and below 0.5 volts in a certain amount of time (may be engine revolutions, I'd have to check the logic).
So two things here - first, the O2 sensor isn't producing the signal the ECU expects, and second, the ECU will ignore the O2 sensor because it thinks it is bad. The ECU will substitute a calculated O2 sensor value.
Will it impact fuel economy? Maybe. If the calculated value is on the rich side, you will use more fuel. If it is on the lean side for your car, the mileage may be a bit better. It won't impact accleration, because under hard acceleration the system runs open loop and ignores the O2 sensor.
The sensor may be absolutely fine, and something else is impacting the signal - like a vacuum leak causing lean running, or a fuel system modification that causes rich running - so much so that the loop that the fuel flow controlled by the O2 sensor can't move the fuel enough to get the sensor into the operating range. The O2 sensor doesn't control fuel flow totally- it just makes minor adjustments to it.
If your plugs look good - not running rich or lean, and the car performs well, then all is good. You will most likely fail any emissions test, should your state have one. No emissions test I know of would even test a car with a CEL.
posted by 192.249....
, Thu, 13 Jul 2006 07:58:26, Thu, 13 Jul 2006 09:31:00 <-- Viewing This Message, Thu, 13 Jul 2006 09:51:52, Thu, 13 Jul 2006 12:56:28, Thu, 13 Jul 2006 11:40:37, Thu, 13 Jul 2006 12:59:45, Thu, 13 Jul 2006 18:35:50, Fri, 14 Jul 2006 07:31:16, Fri, 14 Jul 2006 10:39:23, Fri, 14 Jul 2006 15:07:56, Sat, 15 Jul 2006 19:55:13, Fri, 14 Jul 2006 09:14:51, Fri, 14 Jul 2006 08:58:43
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