I know that this will be a contentious topic once again, but thought I'd toss it out there, to inject some reality into the discussions around coil-packs and spark-plug wires.

First let me say that I am not an advocate of any of the products that use absurd marketing claims to get you to use colored wires or "high-performance" ignition systems. I do not think that aftermarket ignition parts contribute to additional performance. IMHO, the only reason to replace the MINI coil-pack and wires is when they start showing symptoms of failure. Unfortunately, far too many show such symptoms.

Such failures are often manifested by mediocre ignition, causing symptoms ranging from lumpy idle to loss of power, particularly at high-rpm.

Degradation of the ignition components on our MINIs is often slow and unnoticed, but a very high percentage develop such issues - as many as 50% of those he sees, according to George Mehalick. On my car it took three years and 40K miles, before a routine inspection of the #3 coil terminal revealed the dreaded black spot developing.

I replaced the coilpack with an aftermarket version for the same price as OEM. The most noticeable result is that my engine now runs audibly smoother over 6K rpm up to 7200. Idle also seems to be slightly less lumpy. Removing a source of extra resistance in the spark path can explain these results completely.

Regarding the ignition degradation that leads to poor spark, here's my analysis:

- MINI OEM coil and wires use plated steel connectors. For some reason usually on the #3 coil connection first (nearest one to the US driver), black spots will appear on a coil stud. This is a symptom of arcing at the connection, and the black spot is where electro-erosion has etched away the plating layer, exposing the steel pin beneath, and blowing metal and metal-oxide particles all over the inside of the connector. This leads to a high-resistance connection and poor ignition, and cannot be cured by abrasive cleaning of the pin, because the steel pin is exposed thru the plating, and will corrode.

- The initial fault and source of the arcing is not the coil, but failure of the sparkplug wire connector to stay on tight, so while it is necessary to replace the coil, the source of the problem is in the wire. The source is that the spring-loaded connector on the wire is not clamping down firmly enough on the pin of the coil, and this connection eventually loosens under constant engine vibration, micro-sparks, and starts the spiral downhill.

- If replacing the coil due to arcing, then there will be more black gunk inside the terminal on the sparkplug wire than there was on the coil pin, and it will lead to further arcing in the future. At a minimum, when replacing a coil, either use some Deoxit and a q-tip to clean the wire-heads, or replace the sparkplug wires. If you don't replace them, use a tiny screwdriver to tighten the clip inside the wire connector - when I reconnected mine after doing this, it made an audible 'click' when it snapped into place on the coil.

- If you replace the coil with one that has brass terminals, then the terminals can be cleaned with steel wool if the surface ever degrades. The OEM coil terminals cannot be cleaned effectively once the plating has been holed, as they will continue to corrode.

So that's my failure-mode analysis - the wire loosens, causes arcing, and makes a poor connection.

On my car, I replaced with an MSD coil, cleaned out the stock wires, and tightened their connectors. I'll keep an eye on these connections for a few months, now that the plating on the connectors has been holed, and if there are any visible symptoms of arcing again, I'll replace the wires, to get (hopefully) more-reliable connectors than the stock ones that caused this issue. I will not use any brand of wire that makes performance claims.

The MSD coil, BTW, appears to have been made on the same machine as the OEM MINI coil, the only obvious differences being slightly longer towers that the connectors come out of, the brass pins, and, or course, it is somewhat red. It would surprise me if MSD does not manufacture the OEM coil, based on their obvious similarities.

It's worth noting that if you are getting poor ignition performance before replacing spark wires or the coil, you probably will notice performance improvements, but all you are really doing is getting back to the original clean-running again.