COP test question

[bgrd351]

I know that some people use the "swap and find" method to test for a bad COP but since I have possibly 2 bad ones I would like to know if there is a way to test more scientically. I do believe there should be a way to test them with a multimeter but need to know what the values should be and where to test.

 

[Kilgore Trout]

This is in the Haynes manual, do you have one? If not I guess I can go look it up for you...

 

[bgrd351]

well, I havent bought one yet for this car (2002 Gt) and I am out of town right now. I have had a miss for awhile but it was a minor miss. But for the last 2 weeks it has been getting way worse and now that I am 4 hours from Jax at my parents house it is running like crap and I have to drive back today. So, yeah, if you dont mind looking for me it would be great. I checked for codes and it isnt throwing any except P1000 which I understand as no big deal.

 

[Kilgore Trout]

COP primary resistance = 0.55 ohms
COP secondary resistance = 5.5 K-ohms

Remember, when working with the COPs it is always a good idea to use silicone dielectric grease to ensure good dry electrical connection to spark plug. It is also a good idea to clean and condition the COP's rubber boots to prevent water and dirt from getting in the plug wells.

 

[bgrd351]

ok...thank you for that info...but what points do you test from? In otherwords, where do the leads need to go to test primary and where for secondary?

 

[Dragstr05]

Most likely the reason for the coil going bad in the first place is some type of water got inside the spark plug hole. When this happens, the spark will arch inside the boot, and it is visible on the outside when you pull the plug. You may see 2 small dots that look similar to a burn mark, or you may see a line. If this is the cylinder that you are getting a code for a miss, and you see arching on the boot, replace the coil.

 

[bgrd351]

well...this car got a slight miss after I took it back to the dealer I bought it from for them to do some warranty work they promised me whenI bought it and they did a "detail" that they owed me also. From that point on it has had a little miss. But now it is to the point where it shaking and stumbling at idle and rough when up in the rpms like when on the interstate. And to think I am having 3.90's installed this week also so I will be spending a lot more time in the revs

Also, I have looked at each of them and there is no sign of arching so it must have got water inside themselves

 

[Kilgore Trout]

Connect an ohmmeter across the + and the - terminals on the coil where the connector plugs into the coil to check primary resistance.

Connect an ohmmeter across the + terminal and the spring end (spring that connects to spark plug) on the coil to check secondary resistance.

 

[bgrd351]

thank you very much. I had checked two of them across the plug connector and got 0.00 ohms but I see now I had the meter set too high. I will go back and check all of them with the proper setting and correct connections.