Anyone know how to check whether my coils are grounded properly?

I'm troubleshooting my 87 TII's idle bouncing between 1300-1600 RPM's, and one of the first things I noticed was that intermittently there would be sparks dancing all up and down my plug wires. Replaced the wires and no more spark for a while, but still the same problem, and then the other day there were sparks again, but this time only at the junction between the plug wires and my coils, as if the current wasn't getting down the wire. BOTH coils. So I put in different coils this time, and put in new plugs. No more sparks visible but same problem.

On the deceleration portion of my idle bounce it feels like my car wants to stall but then saves itself. Once warm it won't drop below 1300 but while cold it will slip down there and stall if I don't give it throttle. When it does slip down into the 500 RPM range, I swear it's not firing anymore.

I've already checked tons of other crap, though admittedly it could still be an elusive vacuum leak.

So yeah, how can I make sure my coils are grounded right? I've already got a ground strap going from the negative battery terminal to the block, and resistance between the neg bat terminal and the chassis is zero, so that ground looks OK too.

 

They are grounded by the metal brackets they are bolted to. Check ohms between bracket mounting bolts and the negative post of your battery.

 

Hmm ok. Doesn't seem like the kind of ground that would go bad though, does it? Big chunk of metal like that?

 

Not usually, no, but its easy to check.

 

well assuming it's not that, what on earth might cause there to be sparks at the junction of the plug wire and the coil, intermittantly, on both coils? I find it very hard to believe that both of my coils went bad at the same time..

 

Sounds like you're buying poor wires...Not a grounding issue.

 

Yeah you're probably right. Can anyone recommend some good ones? I think I've read 8mm something or other is good. And can I get whatever that recommendation is at an auto parts store?

 

Mazda leads have a fantastic price($30), last a long time, and work very well.