Testing ignition coil 20vt le

Hi everyone

After getting the engine back working, i have noticed the power isnt really there. My mechanic tells me there probably is a faulty ignition coil. It drives ok, but once above 3000rpm, not a lot happens, and when giving it full throttle, the car has a tendancy to need to take its breath. So need to release throttle a bit before it picks up again.

I have got a new Bosch ignition coil, but wanted to know if there is a scientific approach to knowing which coil is malfunctioning rather than just swapping one by one and testdriving?

Thanks!

The traditional way if no codes are available is to let the car idle with one coil disconnected. Disconnect a good coil and the revs drop. Disconnect a "misfiring" coil and the revs rise. Not absolutely foolproof, but if the coil is bad enough to cause misfire, you will identify it.

I disconnected and connected coils with the engine off. I didn't think it was a good idea to do it with the engine running.

There should be 0.4 ohm resistance between the contacts (primary coil resistance). If you have a multimeter you could do this check.

Thanks both, will give it a go!