Hello!

In my attempts to troubleshoot an erratic, or shaky, idle, I've come to test the O2 sensor. I have found a few vacuum leaks, fixed those. Spark plugs are clean and there is no misfire. Car starts easily and throttle response is very good. Along with shaky idle, smog test shows high HC. I just took ownership of this car and am new to Volvos.

The test I performed, per Haynes, was to connect voltmeter between O2 sensor and ground. My results were a constant reading of .82 to .85 V. Ramp up engine speed, voltage drop just a bit, maybe to .75. Never below that, never above .85 regardless of engine speed, even warmed up to temp gauge reading normal at halfway mark.

Test I performed as per Chiltons is to warm up car, attach dwell meter between red test lead on fenderwell by battery and ground. Chilton's says O2 sensor bad if dwell is 54 for the B21F. My dwell at idle swung between 48 and 58. Ramp up the engine speed, and the dwell would change a bit lower then go back to idle reading.

According to all this, my O2 sensor is bad. But I want feedback from the forum, for my mindset is that I'd love to find an easy villian for my idle woes. I don't want to overlook something in my testing methods.

Thanks

Scott in Auburn