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Reysc, You're welcome, I'm glad to help.
Also, you are correct in assuming that your O2 sensor could give you a "False Positive" reading. What happens is that as the O2 sensor approaches the end of it's life, it doesn't produce as much voltage as it did when it was new. Thus it reads a bit low, and the car thinks that it's reading low because the mixture is lean. The car richens the mixture to get a 'correct' reading from the sensor. -and it works, the sensor voltage climbs back up to normal, but now the car is running rich. This cycle continues until the sensor completely dies, and the car can't enrichen the mixture any further. Take note that your sensor can "die a slow death" and cause your car to run rich for a significant amount of time before you can detect the problem with a voltmeter. (For those of you with the 2.4 and 3.1 comptuers, you can still be running rich before the Onboard Diagnostic Computer can see that the sensor has failed, -which wouldn't be triggered until the mixture is already very rich and the sensor voltage still reads low/lean or is entirely dead.)
If you're wondering how to test an O2 sensor to see if it's in the early stages of death, the only method that I can think of would be to have a brand new O2 sensor in the same exhaust stream and compare the readings. If the old sensor reads fewer volts than the new sensor, then it's dying and causing your car to run rich. -but most people probably aren't interested in drilling a second mount for an O2 sensor in their exhaust manifold.
I need to take heed of my own advise and replace my O2 sensor. I just acquired my '87 Volvo 240 a few months ago and I'm getting about 19 mpg when I should be getting 25 or so. We don't have emissions testing in my neck of the woods (Western Michigan area) but I'd bet that this is the culprit of my problems (even though my sensor still reads a correct mixture). I'm driving my '86 Pontiac 6000 in the meantime until I can drop the cash for a new sensor.
Glad to hear your car is on the road, God bless,
Fitz Fitzgerald.
Your previous post (Texas Emission Woes):
http://www.brickboard.com/RWD/index.htm?id=615250&show_all=1
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From your emission numbers, you might be running just a hair on the rich side.
Quote: >> This car has not been running for maybe 6 mos. O2 sensor AMM has been checked and Fuel pressure regulator is new. <<
I wonder if your O2 sensor is dying a slow death. As they die, they tend to read fewer and fewer volts (showing an artificially lean condition). Your computer would richen the mixture to compensate for it. If you're unsure of how old the O2 sensor is or how many miles are on it, it may be time to swap it for a new one. And remember, when changing an O2 sensor, make sure to keep it away from water. (aka, don't change it in the rain). Getting water in these sensors is very bad and can possibly kill a new one before you get a chance to use it.
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'87 Blue 245, NA 214K
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