Exact-Oh
11-15-2005, 11:12 AM
I searched many forums on this issue, with no luck.
I have a '95 540i that is running great... sometimes. Using a Snap-On Solus scanner, the car keeps setting the 203 code (o2 sensor #2) each time it goes into closed loop operation. I can clear the code, but it will continue to reset. The car runs fine for about 20 miles, even with this code set. Then it goes into 'limp home mode', where it has no power and can't get out of it's own way.
I have a hard time believing that these o2 sensors are bad, so I did some further testing. The heated o2 sensors on this car get 450 mV reference voltage from the computer, and output 450 mV duing peak exhaust gas conditions... up to 850 mV when rich, and down to 200 mV when lean. I tested both of my o2 sensors using a Snap-On Vantage o-scope. Both of the o2 sensors are reading approx. the same output voltage. They both seem like they are not updating fast enough, but they are ranging from 350-500 mV on average.
I have checked for leaks on the intake and exhaust side of the engine. I removed all of the decorative covers on the intake manifold and coil-covers, sprayed carb-cleaner everywhere, and did not hear any change in running, indicating no intake leaks present.
I have yet to check the vacuum level in the crank-case, but do have good seal at the cap and dipstick tube. I do have a slight oil-leak, but not even enough for me to care about fixing it... one drop a day when running. Upon searching this, and other, forums, it was suggested that the oil seperator may be the problem. I haven't found any further info on that.
If anyone has dealt with this problem, or has any suggestions, they would be much appreciated. If the car keeps running like it did this morning, I wouldn't even care about the o2 code, but like I said, it totally changes after driving awhile to no power, blowing white smoke from tailpipe, and idling rough until I clear the computer codes. After clearing the codes, it runs great, but the whole cycle starts over. While checking voltages yesterday, I had it idling for at least 1.5 hours, and it still did not run badly, so it must have to be under load for that condition to occur.
Sorry about the long-winded topic, but I really wanted to cover everything I have done, and all of the car's symptoms. Thanks for listening.
I have a '95 540i that is running great... sometimes. Using a Snap-On Solus scanner, the car keeps setting the 203 code (o2 sensor #2) each time it goes into closed loop operation. I can clear the code, but it will continue to reset. The car runs fine for about 20 miles, even with this code set. Then it goes into 'limp home mode', where it has no power and can't get out of it's own way.
I have a hard time believing that these o2 sensors are bad, so I did some further testing. The heated o2 sensors on this car get 450 mV reference voltage from the computer, and output 450 mV duing peak exhaust gas conditions... up to 850 mV when rich, and down to 200 mV when lean. I tested both of my o2 sensors using a Snap-On Vantage o-scope. Both of the o2 sensors are reading approx. the same output voltage. They both seem like they are not updating fast enough, but they are ranging from 350-500 mV on average.
I have checked for leaks on the intake and exhaust side of the engine. I removed all of the decorative covers on the intake manifold and coil-covers, sprayed carb-cleaner everywhere, and did not hear any change in running, indicating no intake leaks present.
I have yet to check the vacuum level in the crank-case, but do have good seal at the cap and dipstick tube. I do have a slight oil-leak, but not even enough for me to care about fixing it... one drop a day when running. Upon searching this, and other, forums, it was suggested that the oil seperator may be the problem. I haven't found any further info on that.
If anyone has dealt with this problem, or has any suggestions, they would be much appreciated. If the car keeps running like it did this morning, I wouldn't even care about the o2 code, but like I said, it totally changes after driving awhile to no power, blowing white smoke from tailpipe, and idling rough until I clear the computer codes. After clearing the codes, it runs great, but the whole cycle starts over. While checking voltages yesterday, I had it idling for at least 1.5 hours, and it still did not run badly, so it must have to be under load for that condition to occur.
Sorry about the long-winded topic, but I really wanted to cover everything I have done, and all of the car's symptoms. Thanks for listening.