coils can be evaluated with a voltohmmeter.

i think it is important to do it with a coil both cold and hot.

first thing is to check for continuity. this will tell you if there is a break in the windings. if there is, the coil be stressed to provide sufficient voltages at speed and load.

it is also important to check for resistance if there is continuity. coil manufacturers will have a spec for this. your coil should measure out within their specs.

personally, i like to put a scope on the secondaries and read demand voltages for each cylinder with the engine at idle. important insights can be gained by running the engine at its max torque rpm.

if you don't have the gear to do this, find a good auto electric shop in your area. they should be able to do this.

alternatively, buy a new coil and see if there is an improvement. do check the coil before installing it, however. you would be surprised how many bad coils are out there in the "new" condition. you might want to do this before you leave the parts counter because often electrical parts are not allowed to be returned - no matter what.

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