Coilpacks and sparkplugs... oh my!

Well, I just spent $277 on coil packs and spark plugs.

I put 360k miles on my VW and never once had this problem. Writing that check was a tough pill to swallow!

One of my Passats is on its fourth set of coilpacks. I replace them all at the same time, they are cheap.

The harder pill to swallow is how much premium gas it has guzzled down in its 230k miles.

Luckily I do not drive it every day.

Why such inferior quality? Material breakdown? Heat being stuffed so close to the head/down in valve cover?

Last weekend I went out and dribbled some fuel down the holly, strung out a lead to the HEI distributor which is original from 1971, bumped the solenoid and it lit right up....been sitting since the early 90s.




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Many modern gasoline vehicles have poor coil-on-plug life spans. VAG is one of the worst, with Ford being a close second. But we see Toyota, Hyundai/Kia, and others frequently. VAG at least has them cheap and easy. They are about $25 each... Ford is around $100, Toyota's coils can be as high as $175 each.

You cannot compare a modern coil pack with an old style ignition system. Completely different. Super rich mixtures are easy to ignite. They do not need a high coil saturation, nor do they fire multiple times during every stroke. Plus, they have nothing to set/adjust/time/check either. So yeah, my Passat may start a random misfire every ~40k miles or so, which I could resolve by just replacing that one cylinder's coil pack (OBD thankfully allows me to do this within 30 seconds without even opening the hood, something 1971 couldn't offer). But chances are you would have needed to fiddle with the ignition system in that old car before then anyway. Most spark plug PM schedule was 20 to 30k miles, if they even made it that long. Not to mention there wasn't anything in 1971 that made 170hp out of 1.8L and met ULEV emissions standards for the 2004 model year.

But yeah, I would like longer coil pack life for sure. But if I do not have to mess with anything else, and have no device called a 'carburetor', I'll gladly spend the whole 5 minutes swapping coils every couple years.

I m still wondering what coil packs and spark plugs are used for? Decorations of some kind?

In my case, they are reminders of why I drive a diesel every day.

BHW Passat = 38 MPG

AWM Passat = 23 MPG (it is a 4mo, though, so there's that, but still...)

Actually, my brother bought a 2009 Mercedes C300. I think he bought it with the intention that I would take care of any problems that arise, keeping him from spending big bucks at the Mercedes dealer the closest of which is over 2 hours away.

He stored it for the winter and after getting it out of storage it skips. My reader says #3 cylinder. So I’ve replaced all the plugs and the #3 coil pack with no change, I just ordered an injector, it looks like I’m going to find out a lot about Mercedes in the near future.

Sadly, there is a lengthy "engine health assessment" TSB for the MB M272/273 engines for oil consumption and misfire complaints. Usually resulting in new cylinder heads.

However, if it were mine, I'd try some BG MOA treatment a few times on it first, then make certain it is filled with the proper 229.51 spec motor oil, 5w40 preferred, with a good filter (Mann, etc.).

Although if the cylinder is "dead", and it still has compression, then you may indeed have something else going on. You can do an output test on the injectors with a proper scan tool. You can also use a stethoscope on them, but if the problem with misfire is NOT the injector, the ECU will cut fuel to it anyway, so you have to clear the DTC, start the engine, and listen right away before the ECU flags the misfire and cuts fuel. Otherwise you'll think it is a bad injector, and it isn't.

Letting a car sit for months on end is not a good thing. I'd tell your brother to try and take it for a spin at least once a month, weather permitting, and try and keep the fuel fresh. Unlike diesel, gasoline starts to go stale in a matter of weeks, and after a month even in a sealed system like a modern car, has already lost several octane points. Ethanol laden fuel is even worse.

I really didn't have intentions of comparing them.

I was more interested in a reason of why a newer pack fails randomly and so commonly.

But it sounds like being so close to the head, and driving copious amounts of voltage several times a stroke, there's no way around it.

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oilhammer said:

with Ford being a close second.

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Yes, this is my V10 motorhome. I had misfires on 5 cylinders. Since it such a PITA to work on (E Superduty) we decided to replace all 10.

oilhammer said:

Sadly, there is a lengthy "engine health assessment" TSB for the MB M272/273 engines for oil consumption and misfire complaints. Usually resulting in new cylinder heads.

However, if it were mine, I'd try some BG MOA treatment a few times on it first, then make certain it is filled with the proper 229.51 spec motor oil, 5w40 preferred, with a good filter (Mann, etc.).

Although if the cylinder is "dead", and it still has compression, then you may indeed have something else going on. You can do an output test on the injectors with a proper scan tool. You can also use a stethoscope on them, but if the problem with misfire is NOT the injector, the ECU will cut fuel to it anyway, so you have to clear the DTC, start the engine, and listen right away before the ECU flags the misfire and cuts fuel. Otherwise you'll think it is a bad injector, and it isn't.

Letting a car sit for months on end is not a good thing. I'd tell your brother to try and take it for a spin at least once a month, weather permitting, and try and keep the fuel fresh. Unlike diesel, gasoline starts to go stale in a matter of weeks, and after a month even in a sealed system like a modern car, has already lost several octane points. Ethanol laden fuel is even worse.

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Thanks Brian I always appreciate your comments and insight into these cars even if it happens to be an "off brand" who drives a Mercedes? Your advise on letting it set for an extended period is duly noted.

jason_ said:

I really didn't have intentions of comparing them.

I was more interested in a reason of why a newer pack fails randomly and so commonly.

...

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Well the broader question would be why do certain items fail and others do not, and what criteria is applied to be acceptable. My dad often gets frustrated when ANYTHING breaks or needs attention, and he seems to be harboring some sort of conspiracy theory that everything is known about and has some secret back door TSB type extended warranty or something. This attitude has gotten worse as he has gotten older, machines such as cars have gotten more complex, and more expensive. What I have to remind him is that t here is a balance between what the consumer can and will pay for, and what would be acceptable to the majority of manufacturers. A Golf is a ~$25k car. Could it be better? Of course. Could we collect all the pattern failure items on it and fix them? Yes. But to what end? Nobody will buy a $50k Golf, even if it never ever breaks.

So it is all a balancing act. Some are better at it than others, for sure. And yes, VAG should be figuring out better, more durable ignition coils. In much the same reason GM should be figuring out how to keep Silverado rocker panels from dissolving after five years, or Subaru from figuring out how to keep the oil and coolant INSIDE the engine. Pick your poison.