02 sensor questions
Race Director
Joined: Sep 2003
Posts: 16,838
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From: Database Error Indiana
True. O2 sensor code means the sensor is reading out of range. It could be reading rich if, maybe the FP regulator was bad and getting too much fuel in the motor. An exhaust leak, sucking air into the pipe can give a lean reading. This would fool the ECM into adding fuel. Then it will run rich and the O2 could still think its lean. Or it could just be a bad sensor, happens all the time.
Thread Starter
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Joined: Aug 2008
Posts: 63
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From: Holtsville NY
True. O2 sensor code means the sensor is reading out of range. It could be reading rich if, maybe the FP regulator was bad and getting too much fuel in the motor. An exhaust leak, sucking air into the pipe can give a lean reading. This would fool the ECM into adding fuel. Then it will run rich and the O2 could still think its lean. Or it could just be a bad sensor, happens all the time.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
I could understand that, the real problem is it only runs like crap in cycles, def think it a sensor. Car runs great on a 30 mile non stop trip with very mixed fuel readings on the screen, sometimes i get my ususal 24 or 28 mpg at 70 mph then at same speed without changing my positin on the gas pedal the mpg shoots down to 8 or 14 mpg, this is when i feel i lose power and it shutters for a bit a lower rpms and then it cycles back to normal like it never happened
It could be an 02 sensor failure. I'd check for intermittent (shorted to ground) o2 wires before you start parts swaping. If you have a good "real time" scanner that shows the sensor values/voltage outputs it should point you on the correct path.
From your description it sounds like the ECM/PCM is seeing a locked in "rich" signal for too long a period of time for whatever reason and is dropping the car out of closed loop as the result until the ignition is cycled or a "lean" signal is seen when you totally get off the gas pedal. This failure should set a "rich' trouble code.
So it it is not a sensor issue my guess is your getting too much fuel into the cylinders.
Done any work on the car lately that you haven't mentioned yet?
Team Owner
Joined: Jul 2004
Posts: 28,462
Likes: 3,288
From: Hartford WI
If that is what you suspect, jack the car up and run it. Check the O2 sensor readings with a scanner. Check the voltage coming out at the wire. Remove the sensor and the readings should change drastically. If it doesn't, sensor could be at fault.
Pro
Joined: Oct 2009
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From: vero beach florida
Team Owner
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From: Hartford WI
Thread Starter
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Joined: Aug 2008
Posts: 63
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From: Holtsville NY
It could be an 02 sensor failure. I'd check for intermittent (shorted to ground) o2 wires before you start parts swaping. If you have a good "real time" scanner that shows the sensor values/voltage outputs it should point you on the correct path.
From your description it sounds like the ECM/PCM is seeing a locked in "rich" signal for too long a period of time for whatever reason and is dropping the car out of closed loop as the result until the ignition is cycled or a "lean" signal is seen when you totally get off the gas pedal. This failure should set a "rich' trouble code.
So it it is not a sensor issue my guess is your getting too much fuel into the cylinders.
Done any work on the car lately that you haven't mentioned yet?
From your description it sounds like the ECM/PCM is seeing a locked in "rich" signal for too long a period of time for whatever reason and is dropping the car out of closed loop as the result until the ignition is cycled or a "lean" signal is seen when you totally get off the gas pedal. This failure should set a "rich' trouble code.
So it it is not a sensor issue my guess is your getting too much fuel into the cylinders.
Done any work on the car lately that you haven't mentioned yet?
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Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
I did the complete opti, plugs, wires, wp and stat, all delco parts no aftermarket. I do not have this scanner you are referring too. I just pulled the codes and planned on replacing what the car told me it needs. Funny thing is until I repalced all these parts and it has only been 10 days is when all this happened, the reason I did all the work was i had a leaky waterpump dripping on Opti and the car has 105k so i figured its time to replace all, I was not expecting this to happen. What should i do? I was prepared to buy two new sensors before the cats
I was just thinking out loud what would cause a "rich" condtion other than an intermittent failing O2 sensor. Replacing the 02 would be the cheapest of the solutions presented so if you find no faults with you existing 02 you might want to swap that out with a new one.Check for shorted wire/s to that sensor is still a good place to start before replacing the sensor though.
Here is a thought: I'm not for sure off hand if the o2 on the left exaust bank is the same as on the right exaust bank if they are you could switch them and see if the problem shifts with the sensor. Maybe someone will chime in on this...
Opti related thoughts: I'd check for spark on the odd bank(driverside) plugs. Perhaps there is a plug not firing properly on that bank or recheck the plug wire placement....it is easy to mix those up and get an out of sequence firing order.
Melting Slicks
Joined: Aug 2008
Posts: 2,082
Likes: 50
From: Palmdale CA
Example...I had an 02 sensor "trouble code" on a Mazda one time that turned out to be an Air leak in a bellows, just aft of the MAF sensor.
Make sure you look over your work closely before buying more parts...
Thread Starter
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Joined: Aug 2008
Posts: 63
Likes: 0
From: Holtsville NY
Sorry I didn't get back sooner...work get's in the way sometimes. You could very well have a sensor problem, but the problem accured after other work was performed, and this would make me Suspicious.
Example...I had an 02 sensor "trouble code" on a Mazda one time that turned out to be an Air leak in a bellows, just aft of the MAF sensor.
Make sure you look over your work closely before buying more parts...
Example...I had an 02 sensor "trouble code" on a Mazda one time that turned out to be an Air leak in a bellows, just aft of the MAF sensor.
Make sure you look over your work closely before buying more parts...
Thread Starter
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Joined: Aug 2008
Posts: 63
Likes: 0
From: Holtsville NY
Checking for trouble codes was the right move to make.....you did good I was just thinking out loud what would cause a "rich" condtion other than an intermittent failing O2 sensor. Replacing the 02 would be the cheapest of the solutions presented so if you find no faults with you existing 02 you might want to swap that out with a new one.
Check for shorted wire/s to that sensor is still a good place to start before replacing the sensor though.
Here is a thought: I'm not for sure off hand if the o2 on the left exaust bank is the same as on the right exaust bank if they are you could switch them and see if the problem shifts with the sensor. Maybe someone will chime in on this...
Opti related thoughts: I'd check for spark on the odd bank(driverside) plugs. Perhaps there is a plug not firing properly on that bank or recheck the plug wire placement....it is easy to mix those up and get an out of sequence firing order.
I was just thinking out loud what would cause a "rich" condtion other than an intermittent failing O2 sensor. Replacing the 02 would be the cheapest of the solutions presented so if you find no faults with you existing 02 you might want to swap that out with a new one.Check for shorted wire/s to that sensor is still a good place to start before replacing the sensor though.
Here is a thought: I'm not for sure off hand if the o2 on the left exaust bank is the same as on the right exaust bank if they are you could switch them and see if the problem shifts with the sensor. Maybe someone will chime in on this...
Opti related thoughts: I'd check for spark on the odd bank(driverside) plugs. Perhaps there is a plug not firing properly on that bank or recheck the plug wire placement....it is easy to mix those up and get an out of sequence firing order.
Le Mans Master
Joined: Jul 2007
Posts: 5,043
Likes: 8
From: Tampa Florida
2 last questions for now: did you go back with the same temperature T stat or did you go cooler? What is the coolant temp read on the cluster when the code is set?
Last edited by engle1147; Feb 26, 2010 at 06:05 PM.
Thread Starter
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Joined: Aug 2008
Posts: 63
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From: Holtsville NY
Great question, same stock stat, no mods what so ever. The temp runs at 180 or 185 at normal driving, it never moves unless it sits for a bit on idle but even then the fans kick on and i have never seen it over 210 in the summer traffic
