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 Posted: Jan 27, 2020 09:06AM
 Edited:  Jan 27, 2020 10:35AM
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Understood, but what could cause both sensors to go out of range (they drop to almost 0V) at idle? Also, once they drop to 0V, they stay there until I restart the car, then they return to the normal range (.1V to 1V). Thanks again.

 Posted: Jan 27, 2020 06:42AM
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Quote:
Originally Posted by rodolfo2110
I borrowed a Foxwell NT510 to read the values of the O2 sensors and see if they were working correctly. Before starting the engine, both sensors slowly increased to about .42V. I then started the engine and started driving. Sensor 1 fluctuates between .1V and .8V, and sensor 2 was pretty steady around .8V. Car seemed to be running fine (despite check engine light being on). Then I came to a stop sign and slowed down. As soon as I came to a full stop, both sensors dropped to .01V, the check engine light started flashing, and the engine started running rough. The sensor voltages never rose after that even after I accelerated. However, if I turn off the car and start it back up, the sensors go back to working as listed above. Any thoughts on what could be causing this drop to 0V for both sensors at idle?
Normal operating range for both o2 sensor signal is between 0.1v and 1.0v. The heater circuit goes higher but not the signals.

 Posted: Jan 23, 2020 10:20AM
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I borrowed a Foxwell NT510 to read the values of the O2 sensors and see if they were working correctly. Before starting the engine, both sensors slowly increased to about .42V. I then started the engine and started driving. Sensor 1 fluctuates between .1V and .8V, and sensor 2 was pretty steady around .8V. Car seemed to be running fine (despite check engine light being on). Then I came to a stop sign and slowed down. As soon as I came to a full stop, both sensors dropped to .01V, the check engine light started flashing, and the engine started running rough. The sensor voltages never rose after that even after I accelerated. However, if I turn off the car and start it back up, the sensors go back to working as listed above. Any thoughts on what could be causing this drop to 0V for both sensors at idle?

 Posted: Nov 14, 2019 11:06AM
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The pre and post sensors are the same units - you might try swapping the two to see if the errors change.

 Posted: Nov 14, 2019 09:00AM
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No, the cat and O2 sensors have never been replaced. Is there a way to check if that's the issue though? I read one thread that replaced the post O2 sensor and resolved his issue, but I also read quite a few more threads where they tried that and still had the same code. And thanks! I hope to keep it running for quite a few more thousand miles!

 Posted: Nov 14, 2019 04:08AM
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Here are some error code definitions:

P0907 - Post Catalyst Fuel Trim System too rich (Bank 1)
P0304 - Cylinder 4 Misfire Detected
P0313 - Misfire detected with low fuel

Given the high mileage on your MINI (congrats on getting over 200k!), the first thing I would question is the condition of the catalytic converter and the o2 sensors before and after the cat. Has the cat or the sensors ever been replaced?

 Posted: Nov 13, 2019 02:37PM
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Not sure if it's related, but the constant mpg on the display was stuck at 99.9 for a while, which led me to believe that I was actually getting better gas mileage with Techron. I recently filled up the tank again though, and it hasn't stuck since. I tried to see if this ever happened to anyone else, but haven't found anything yet. Thanks again for any advice!

 Posted: Nov 13, 2019 09:09AM
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Hi everyone, I drive a 2004 Mini R50 w/ auto transmission (208,000 mi), and I started getting a check engine light with P2097 code in the summer. The first couple of times I was able to clear it, but now it comes back right away. I didn't notice any kind of performance loss or mpg drop, so I didn't think much of it. Now that it's fall and I am no longer running the AC, I started noticing RPM loss at idle. If it sits long enough, the engine light will blink and it'll throw a P0304 (cyl 4 misfire) code, but as soon as I start driving again it runs fine. Once I also got a P0313 code, but never since.

I replaced all spark plugs and wires, and swapped in a new coil pack. I replaced the air filter and ran Techron fuel system cleaner through the tank. I also reset the ECU and the BCU. But nothing has helped so far. Has anyone run across this before? If you can point me to an existing thread or share what else I should try, I would really appreciate it! Thanks in advance!