My 1985 325e recently failed smog. I replaced the cat and aft portion of the exhaust last year and passed smog with incredibly low emissions measurements thanks to the new catalytic converter. Now, just over a year later, I failed thanks to high NOx PPM at 25 MPH in 2nd gear, with the reading nearly double the allowable max.
The car is unmodified from stock, and recent maintenance performed before smog included an oil service, replacement of both crankshaft position sensors with Bosch units, a fresh air filter and a new air intake boot, as the old one had a tear which was allowing un-metered air to enter the system after the sensor.
Considering that I've replaced a number of other sensors, that the engine runs well and starts with ease whether cold or hot, and that my Co2 readings were also high, I am suspecting the oxygen sensor.
I suspect my E30 has close to or more than 300,000 miles on its original M20B27, and I think the oxygen sensor might be original as well, because it is a BMW unit and the color-coded wiring matches what's listed in the ETM.
So, I performed Pelican Part's oxygen sensor test a few times yesterday and this is what I recorded. I lost contact with the sensor's green signal wire a few times, but the video still shows a roughly expected voltage range, which changes when I rev the engine or remove the oil cap to change vacuum pressure. Also, the sensor voltage with the ignition on but the engine off was a steady .463 volts.
I have an idea that my car may have passed the first time with such ease because the hole in the intake boot was allowing fresh, un-metered oxygen into the engine. The tear in the boot became large enough to cause rough running after my air filter replacement made it worse, so I replaced it, which effectively sealed things off, allowing no fresh air to enter the intake after the sensor.
Any help is greatly appreciated!
The car is unmodified from stock, and recent maintenance performed before smog included an oil service, replacement of both crankshaft position sensors with Bosch units, a fresh air filter and a new air intake boot, as the old one had a tear which was allowing un-metered air to enter the system after the sensor.
Considering that I've replaced a number of other sensors, that the engine runs well and starts with ease whether cold or hot, and that my Co2 readings were also high, I am suspecting the oxygen sensor.
I suspect my E30 has close to or more than 300,000 miles on its original M20B27, and I think the oxygen sensor might be original as well, because it is a BMW unit and the color-coded wiring matches what's listed in the ETM.
So, I performed Pelican Part's oxygen sensor test a few times yesterday and this is what I recorded. I lost contact with the sensor's green signal wire a few times, but the video still shows a roughly expected voltage range, which changes when I rev the engine or remove the oil cap to change vacuum pressure. Also, the sensor voltage with the ignition on but the engine off was a steady .463 volts.
I have an idea that my car may have passed the first time with such ease because the hole in the intake boot was allowing fresh, un-metered oxygen into the engine. The tear in the boot became large enough to cause rough running after my air filter replacement made it worse, so I replaced it, which effectively sealed things off, allowing no fresh air to enter the intake after the sensor.
Any help is greatly appreciated!
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