Coil pack failure (again!)

[batteryman]

Hi, we have a 2004 1.4 FSI polo with only 41,000 miles on it. It's just had the coil packs replaced again, third time since they were done in 2011. They were replaced in 2011 and failed again within about 9 months. The car's just been in for an intermittent misfire and all 4 packs were replaced yet again - it's now running fine.

Can anyone explain why they should fail so often?

[itavaltalainen]

Which coils were fitted now?

Genuine VW or cheap aftermarket?
VW had issues with some coils.... if you got them cheap (e.g. off Ebay for a really good price) they may be ones from this bad batch?

There are better coils available, a lot of people fitted Audi R8 coil packs which seem to be better. What is you engine code?

[batteryman]

Thanks for the reply.

I don't know which packs are fitted, only that the original ones failed at about 30,000 miles and there have now been three replacements. On "normal", old fashioned coil/distributor systems, the only part which would usually fail was the distributor cap - usually due to tracking. The VW coil pack system seems troublesome in my experience and I wondered what experience other VW petrol users had.

[SammoVWT]

From my electrical knowledge, if your coils are blowing that frequently - somthething else is causing the coil to draw more current than it should.

It can be anything from bad grounds/terminals, to bad leads and plugs - the coils are rated for a certain power output. If your spark gap has say increased by 50% (or difficulty to induce spark correctly to over come drains on system), you will need a considerably higher voltage for the sparkplug to discharge correctly, or failing that it will pull more current as the coil will start to discharge at a higher power for successful ignition - all these things will wear out the coils faster, mostly due to heat.

Engineers spend a significant amount of time testing these things at rating, and will only be guarunteed for that rating, anything that alters this spec generally causes the lifespan to shorten.

Of course this doesnt account for aftermarket parts with poor quality build/materials.

Typically I have only ever had problems with coils when i've neglected the ground points in my engine bay which have been allowed to accumulate with grime. Probably not so much an issue with newer cars as they have undertrays more or less as standard, but it doesnt stop the grime that flies through the radiator fan.

If you could slap a giant heatsink on the thing it would buy time, but the conductors break down, and then the insulators and then dead coil.

Also forgot to mention, as cars age - wiring insulation becomes an issue. Keep an eye out to check there are no shorts, these can lead to problems if left neglected. Just keep an eye on things, theres also every chance you could have just had a bad batch of coils. It happens from time to time.