Still diagnosing what is wrong with my Alfa 164. I'm starting to think I may have a bad coil pack. How do I test an individual coil on plug pack with a multimeter?
I've also read elsewhere that a non-contact voltage tester might work on a running car. Has anyone ever tried this? I'd rather test the coil packs while they are off the car because the rear bank is inaccessible when the engine is running. The intake plenum is in the way and takes a while to remove.
They test just like any other coil. heres a you tube link. hard part is finding the specs http://www.youtube.com/watch?v=rRQ45lT2d3c
Ohm it out like any other and look for evidence of arcing? Typically something like 10000ohms on the secondary and under 100 on the primary.
Depending on the problem I think you might be able to disconnect/reconnect each coil while the engine is running and see which one has no effect on the running on the engine.
I think all you can do with a multimeter is check the resistance of the windings. A close visual inspection of the coil boot is a good idea and if they're cheap enough i'd just replace all of them.
There's not much else you can do without it running. The easiest thing to do, if the problem is consistent, is put the car back together, run it, unplug the front coils while it is misfiring, and see if any cylinder causes almost no change when unplugged. If all the front coils cause a big change, you can swap the front and rear coils and then find the bad coil while it's on the front by unplugging. That's tedious.
But absent a misfire counter or monitor in OBD datastream or an oscilloscope to watch the primary circuit behavior and compare between coils (also tedious but doesn't require removing plenum), it seems like you have to put it back together and take it back apart at least once at this point, unless you get lucky and put the problem coil(s) on the front.
If you have an IR pyrometer and can see the rear exhaust manifold you can try getting it to misfire consistently and then look for the exhaust runner that is cooler than the rest. That would be a clue.
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