testing a coil?

[falcon fanatic]

So i did a cam install on my car and put it all back together and it seems to run strong and make more power accross the powerband than before (though maybe not as much as it should?). It pulls hard to at least 5K and it is smoother than with the stock cam at high revs. HOWEVER, I cannot get the bugger to idle except with the idle speed screw all the way in (weber 38/38), and then it idles like doo-doo. Kind of rough and sputtery.

Haven't been able to trace a vacuum leak, although I'm not ruling that out yet. I welcome suggestions on further testing for that. However, I also think I should test my coil since it also acts a bit like a weak coil. How do I do that using a multitester??? :

 

[JackFish]

Did you verify the cam specs?

 

[Lazy JW]

...... It pulls hard to at least 5K.....

Weak coil won't do that.

Set your ohmmeter on the lowest range; primary resistance will be less than 5 ohms, maybe as low as .5 ohms. Secondary will need a higher scale on the meter and will read around 15,000 ohms. Or 5000. or 20,000. Best to have a known good coil to use as a comparison.
Joe

 

[jamyers]

Yup, a weak coil can often idle all day long, but drops out under load.
I'd chase down that vacuum leak before digging into anything else.