Checking A Faulty Coilpack? Car's Dropping Cylinder Randomly

[Dani Boi]

When driving, my car will drop a cylinder making it sound like a wrx which I'm sure is to do with my YJ coils I bought a year ago (just changed spark plugs and it's still doing it). The problem is that it only happens randomly as it can happen within 5 minutes of driving or 30 minutes of driving which makes it inconvenient. Is there any way you can tell if the coilpack is faulty by just looking at them? Perhaps driving around at night with the coilpack cover off and seeing if it shows spark? Any ideas?

Edit: If I pull over when it drops and start the car back up, it will return to normal

Edited July 31, 2013 by Dani Boi

[GTSBoy]

Visual inspection of the coilpack will show up and cracks or carbon tracking across the outside, but given that they're only a year old, they probably haven't suffered the sort of age related failures that you can see.

Best bet is probably just to find a set of known good other coils and either swap them all out and see if the problem goes away, or keep swapping them out one at a time until the problem goes away. Whichever way you go about that you will end up swapping one coil at a time if you're trying to find which one is at fault.

[niZmO_Man]

Stopping and starting the car resets the ECU. Doesn't sound like coil packs to me.

[iruvyouskyrine]

My old RB20 used to drop a cylinder every so often and restarting it did fix it most of the time. And it was caused by a faulty coilpack. Swapped them out with a known good set and it never happened again.

[jhjones]

maybe coil loom?

[Guilt-Toy]

take the cover off coil loom, drive the car until it starts missing, then disconnect each cyl one by one.

one of them you will notice that the engine sound will not change, that is the cyl that you are having issues with. remove the coil pack at a later date and check the loom, also check the injector connector for that cyl too.