My 92 960 started misfiring a couple weeks ago. I've been busy with work and didn't have a chance to check it until today. Unplugging each coil, one by one, showed that the #4 coil seemed to be out. There was no change in the idle when I pulled the #4 coil, whereas I there was more stumble when I pulled each of the other ones. In addition, when I put the coil end next to the head, I saw sparks jump, but nothing with coil #4.

So first, is it safe to say that the #4 coil is dead? I remember there being a way to check the coils by measuring resistance. However, with my digital meter, I read about 220-240ohms for each coil. No difference between #4 and others.

Next thing... I started the car, and checked the voltage on the O2 sensor output. It didn't fluctuate, but I'm not sure what the "refresh" rate of my multimeter is either. However, it read a voltage of about 0.6. Is there any other way to check whether my O2 sensor is still good or not, short of an oscilliscope??

Thanks

To make sure it's the coil and not the power stage, switch teh two power stages and see if the #4 still has no effect or if it swic=tches to a different one.
If your meter is a bit slow to fluctuate ( make sure it's on manual scale setting and not auto range) try one of those cheap analog meters, the sweep is obvious on those
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '82 Mercedes 300SD

switch power stage by plugging the #4 coil into one of the first cylinders, yes?

I will try that and the analog voltmeter tomorrow. Thanks

I believe ( without looking in th egreen manual I'm too tired right now ) that one power stage runs #1, 3, 5, an dthe other runs 2, 4, 6. You'd need to switch the powe stages to know for sure( Although I suppose you could swap 2 coils out )
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '82 Mercedes 300SD