Can u test coils to see which one is bad?

[kfisher777]

I know I have a few bad coils but aside from reading any codes it would have thrown for misfires...can you test the resistance to see if its bad? I've pulled six of them so far and all but two of them, including a new one I just bought, show a resistance of 5.4 to 5.6 and the different ones show 6.4 and 6.5. Is this an accurate enough way to determine that those two are bad? Any help would be greatly apreciated.

 

[kfisher777]

by the way, I was doing the testing with a standard multi-meter set on ohms/resistance. I really hope this is a good way to test these coils because I can't spend the money to pay the dealership to do it. Any suggestions would be greatly appreciated.

 

[Alax7]

my dad is an old school mechanic not good with little gadget that tells you if its good or not but he knows the mechanics behind cars. he checked mine when the dealer said we had bad coils. There are two things he he. One if the coil is bad the car misfires and you now how that sounds and feels so when you pulled a bad one the car will remain the same since you removed a coil that wasn't working but if you removed one that was good the shaking and sound will get worse. Thats a little harder to tell if you have a coil that hasn't gone completly bad. Heres the ohter thing he did. You can pull the coil out a little to where it still fires into the engine. you'll be able to hear the spark being fired clearky. On a good coil you'll hear it firing evenly but on a bad coil you'll either hear misfires or it not firing at all. We saved a lot of money doing it ouirselves because the dealership wanted to charge 800 for labor plus a few hundred for coils. they said it was 7 coils going bad but it was only three and thats how we found them.hope it helps

 

[joegr]

The problem that these coils get is that they have internal high voltage break down. You can check that with an ohm meter.

 

[kfisher777]

The problem that these coils get is that they have internal high voltage break down. You can check that with an ohm meter.

Thats what I did and got a reading of 5.5 ohms on five of the coils and 6.4 ohms on the other three of them. That has lead me to believe that those three with the higher reading must be the bad coils. Do you think that is accurate?

 

[LongIslandLSE]

do what alax said, pull one out at a time. when you pull one out if the car remains the same thats the one, if worse put it back in. or just buy a new set because they are all gonna go bad soon, just easier.

 

[joegr]

Thats what I did and got a reading of 5.5 ohms on five of the coils and 6.4 ohms on the other three of them. That has lead me to believe that those three with the higher reading must be the bad coils. Do you think that is accurate?

No.
Those resistance measurements are telling you nothing. Those readings are all within spec. The meter you used measures resistance at only a few volts. The break-down problem happens at several thousand volts only.
I say again, you can't test for this issue with a resistance meter.

You can test them, on the car, under stress, using an oscilloscope. You look at the waveform caused on the primary of the coil when the magnetic field collapses.