Flashing Check Engine Light & Coil Pack (MK4 Jetta)

In Spring 2013 I was driving to the gym and all of a sudden my Check Engine light (CEL) began to flash (orange color). My car began to stutter and vibrate unnaturally. Immediately I pulled over and turned off the car.  I waited about 1 minute and turned the car back on– the CEL was still flashing yellow and the car was stuttering. I decided to go to the gym and come back after an hour to try and turn it on again. When I came back the car was no longer stuttering! But the CEL light remained on (wasn’t flashing though). I took the car back home in Toronto and drove it for a week without issues. The car would stutter a bit only on start-up but would go away once the engine temperature rose.

I noticed the problem with the flashing CEL / engine stuttering would usually only come up on a cold engine and when it was moist outside (after rainfall or light snowfall in the spring).

After a week I drove back home to Windsor (about a 250 mile /400km drive) without issues.

When I got home the first thing I did was scan my car. I was getting codes for Cylinder #2 misfiring and short to ground codes for the cylinders.
Upon some investigation and research it turned out to be the Coil Pack. Physically, the coil pack from the outside looked fine, but upon closer inspection I noticed fine hairline cracks (very small). I found the majority of the cracks around the 2nd input for the ignition cable, which also matched up with the Cylinder #2 misfire. The were some other cracks around other ignition lead inputs as well.

Cracked Coil

My first attempt at fixing this was covering the cracks with epoxy. This seemed to work but about a month later I was washing my radiator and engine bay and upon start up the car up the car started to stutter and the CEL was flashing. At this point I gave in and bought a new coil pack from AutoZone(~$260 USD).

These cracks were so small that you wouldn’t notice them unless you unscrewed the coil pack and took the unit out and examined it closely under light. The fine hairline cracks was all that was needed to create tiny electric sparks in the dark that caused it to short.Ever since replacing my coil pack and ignition cables my issue with the flashing CEL and stuttering has been resolved.

Parts needed (VW part numbers):

06A-905-409-N  –  IGNITION LEADS (Cables)

06A-905-097  – COIL PACK


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