The truth about coil packs

[pingu81]

Thread Summary: Just because a coil passes the "resistance test", do not trust it.

I have a 91 with 100K miles which I picked up last December. It was driving fine until the other night when I experienced lack of power and backfiring at idle (after the car has been warmed up). Further investigation lead me to take off the valve covers to inspect the coils and plugs. The front bank of coils and plugs were fine. When I took the rear bank spark plug cover off I found this:

The screws holding down the coil pack for the cylinder closest to the passenger side were not tight AT ALL. In the pic you can see the exposed threads on the bolts. The middle cyclinder was not as bad, but still had loose bolts. I tightened everything down in the rear bank then went for a test drive. I still had the problem.

After being puzzled once again, I decided to do the resistance check on the rear bank of coils and at the same time check out the plugs. As I took out the coil pack, water came out with it. I guess that was from washing my car. I suspected this was the problem. I let everything air dry. Before putting everything back together, I checked the plugs and coil packs. Plugs were ok. Coil pack for the cylinder where the water came out of it had a bit of rust on it. It measured 1.09 ohms.

I then put everything back together and took it for a test drive. This time, the lack of power was still present. The backfiring was present, but not as bad as before. This lead me to believe that the coil pack was bad. I went to the dealership and picked up a new coil pack and popped it right in. THE PROBLEMS WENT AWAY.

Moral of this post. For those of you who say if coil packs pass the "resistance test", pop them back in, think again. Somehow the one I got must have corroded away in the inside as well from the moisture.

I'm glad I fixed the problem and my car is back on the road again.

 

[Jin1976]

Don't forget to get new gasket for the coil covers.

 

[Daedalus]

I have posted the same at least a couple times, though some did not agree. The packs are subject to internal acing when they get old, often due to tiny cracks in the thin insulation separating the copper coils.

 

[nsxtcy85]

Coil packs cant jump to high resistanc if they are defective because of temperature.

 

[BioBanker]

So when you say that you believe that the water got in there from washing your car, you mean washing your engine bay, right?

I use a waterless foam to wash back there to avoid issues like this. Spray it on, wipe it off. No water.

 

[AR]

Is not from washing the engine, but from washing the car and rain too. Honda made a mistake in the design of the RWG and the rear of the engine bay.

 

[UnhuZ]

Bio, no...actually the water gets there by falling down through the rear window garnish....

http://www.nsxprime.com/forums/showthread.php?t=104407

http://www.nsxprime.com/forums/showthread.php?t=104635

http://www.nsxprime.com/forums/showthread.php?t=92915

in this last one, pay attention to what i write in the first post of the 2nd page (post #51 on that thread)

 

[Briank]

Ignition coils are very simple and robust electrical devices.

Water in and around the spark plug and the end of the coil pack provides a path for high voltage to go someplace other then the spark plug. Once this happens it creates a carbon path that can conduct even when the water boils off. Corrosion at the plug also adds to the conductivity adds to the problem. Ohm measurements are just checking the primary windings of the coil and does not disclose any problems with the high voltage secondary of the coil.

I believe if the boot of the coil is thoroughly cleaned and dried and coated with dielectric grease or ignition sealer the problem can be fixed with out replacing the coil.

http://www.gunk.com/CAT_M406.asp

 

[m3456y]

Ignition coils are very simple and robust electrical devices.

Water in and around the spark plug and the end of the coil pack provides a path for high voltage to go someplace other then the spark plug. Once this happens it creates a carbon path that can conduct even when the water boils off. Corrosion at the plug also adds to the conductivity adds to the problem. Ohm measurements are just checking the primary windings of the coil and does not disclose any problems with the high voltage secondary of the coil.

I believe if the boot of the coil is thoroughly cleaned and dried and coated with dielectric grease or ignition sealer the problem can be fixed with out replacing the coil.

http://www.gunk.com/CAT_M406.asp

+1 on the dielectric grease.

The best $5 investment you can make, in my opinion. I've used it and recommended it to many people with engine misfiring problems. I use it in my NSX and both my Legends. It's become part of the spark plug changing, tune-up process on every car I own and work on.

 

[Lime Green NSX]

Can anyone tell me what the difference is on:

dielectric grease

verses

dielectric silicone?

they both can be used on igintion systems.

thanks cheers!

 

[pgilliam1]

I soak down the coil completely, inside and out with silicone spray. Let it dry and wipe off any excess. Keeps em good as new :smile:.
Happy Motoring!