RKA

Okay, I asked this on the 12v forum this AM. No answer yet, so lets see if anyone here knows the answer. FYI, I'm talking about another car below...but for all purposes, assuming it's similar to the ignition system on the 12v and 30v A4's. 3 ignition coils supply spark to 2 cylinders each. The wire carries spark directly to the plug. No coilpacks.

Let's suppose one of the ignition wires got old and rotten...eventually leading to the point where there was infinite resistance between each end of the wire (resulting in a misfire condition for an unknown period of time). Is it possible that the ignition coil might be damaged if the spark energy doesn't make it to the plug?

James R.

I think the excess spark energy will just go into the other plug that is still connected. They do that thing with the 2 cyls per coil by taking advantage of the timing of the combustion cycles such that you're actually sparking in two cyls, but on one it's wasted during the exhaust stroke right?

RKA

I had zero spark on 1 cylinder (my mother's car). Plug was okay, but I replaced it, wire had no continuity, so that was replaced as well. The spark on that cylinder is still iffy compared to the other 2 on this bank (replaced all wires and plugs on the bank anyway). So I was thinking the coil might be damaged.

When I get to the rear bank of cylinders, we'll see what the sister cylinder is doing. I think my father is going to pick up a spare coil anyway. I was hoping the answer would be "yes, the coil will get damaged".

James R.

well I've never looked at the anatomy of those dual plug wire coils, maybe the end closest to the coil itself is corroded from arcing to some piece of metal close by? Could happen ya never know.

I'm just taking a guess, that there's only one coil inside of that thing right? And that single coil goes to two cylinders. If that's the case how could that coil work fine for one of the two and not ok for the other.

Regards,

James R.

RKA

Each operates a cylinder on opposite banks. I've only looked at one bank. After changed out the plugs and wires on bank 1, there is still a considerable degree of misfiring, so that weak spark in the cylinder I worked on, might correlate to a weak spark on a cylinder on the opposite bank. We're going to try a new coil to see if that helps...I'm assuming that changing the wires and plugs on the other side won't do a damn thing (even though I'm going to do that anyway. I'm also assuming we'll find the sister cylinder with a weak spark as well.

I'm just trying to establish some cause and effect, but this might just break down to age. The car is 16 years old, with 240K on the clock. It spents it's time making 3 mile trips back and forth to the grocery store, and that's it. The plugs have been changed sometime in the last few years, and the three I pulled looked great. My father can't remember when he changed the wires last, so they are suspect, and the coils are all original.

RKA

Misfiring stopped when I got the new ignition coil installed.

Now the car stalls out when it's warmed up (idle air control valve I think)....