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Another emissions failure, bad O2 sensor? Posted by Baab [Email] ![]() ![]() ![]() |
Took my '86 900S through the "enhanced" dyno emissions test today. Failed for slightly high HC and very high (several times over limit) CO. NOX is very low. So the car is obviously running too rich, though there are no overt symptoms. (No odor or black smoke, no rough running, gas mileage has been OK.)
The car aced this test the last time, but that was before replacing the AMM with a rebuilt unit which I did not adjust since the car ran perfectly with it right out of the box. Therefore I thought I'd start there first. (Plugs, filters, wires, cap, & rotor are all recent.)
What I'm finding is that the O2 sensor is putting out a constant +.48 volts no matter what the AMM setting is. I've tried adjusting several turns in each direction, no difference, always a constant voltage with little or no fluctuation from the sensor. It also makes no noticable difference in idle quality when the O2 sensor is disconnected, and voltage remains the same. (So for now I've set the AMM back to 390 ohms which is where it was before the adjustments. I had it down to about 200 ohms and up to about 600 during testing.)
Looks to me like the O2 sensor has probably bitten the dust. Just wanted to check for other possible causes or other tests I should try before replacing it. (The car has a "universal" 3-wire Bosch sensor that I installed about two years ago.)
posted by 209.92.6...
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