Coil packs how long do they last?

[DrRobin]

I have had a slight rough running since August when I changed the CATs on a 2001 2.7L with 92,000 miles.

At first I got the odd misfire, but it was on a different cylinder and only happened at low revs after deceleration. My code reader said all four O2 sensors were slow to respond, so changed them but it didn’t make much difference.

I still got a misfire, about twice a week, but could avoid it if I kept the revs up or played the throttle a bit after deceleration and before feeding in the power. The misfire went when I fully charged the battery, but the car still didn’t run all that smooth, especially when warm.

After cleaning the throttle body, this improved it, so last to check was coils and plugs. After stripping out bank 1 last weekend the plugs all looked fine and I cleaned the coils, but noticed that two had a hairline crack. This weekend I obtained new coils and plugs and changed all six. The car is now running great, back to how it always was.

Looking at the coils all six had at least one hairline crack, they were Beru and changed at the main dealer at 55k miles (2009). The car now has 93k miles.

So my questions are

-Is 40-50k miles or 10 years about right for coils? It seems quite short, I would have expected 80-100k.

-What causes the coil to fail? Excessive heat?

The plugs were all fine, I can’t see on any of the receipts when they were changed, but it wasn’t in the last 6 years or 20-30k miles.

What is your experience?

Robin

[JFP in PA]

Depends upon many factors; environment, amount of heat exposure, who's coils, etc.

At 10 years, you got your money's worth..................

[PaulE]

Well I'm the original owner of my 2003. My original coil packs developed some cracks at 30,000 miles, they were replaced and the replacements went at 60,000 miles. I'm now at 96,000 miles and the third set are still going strong, so I consider myself lucky.

[paulofto]

I must be very lucky. My 2003 S has just under 120,000 km or about 75,000 miles and unless the previous owner changed them, which I doubt, it has the original coils. It had about 45,000 miles when I bought it. I changed the plugs at about 60,000 miles and inspected the coils but found no issues. In my 8 years of ownership I have never had a misfire of any kind. The car is driven from April to October (it’s being put to bed today for the winter).

Perhaps never being exposed to salty roads or harsh conditions makes a difference but it sounds odd to me that coils need replacing as often as they do for some cars.

[Rob175]

I own a 98' with 92,000 miles. I bought it in 2003 w/35,000 miles and to my knowledge the coild have never been changed and my summer driving only Boxster is running great.

The only issue I have is periodic static on AM radio stations. It comes and goes and increases with speed. It's sounds like the static one can get from "non-resister" plugs but since it comes and goes I don't think the plugs are the issue......maybe a crack in a coil??......I have no idea....but since I'm mostly listening to FM it not a big issue.

[Jgkram]

I too have never replaced my coils and believe they are original. I own a 2001 2.7 with 67K on the odometer. It's a daily driver and lives outside. I did replace the plugs at 45K but that was it. I knew purchasing a Porsche was going to be a pricy thing but it never ceases to amaze me how much attention these cars can require in comparison to others. I still get more enjoyment from it than anything else but as it ages... It's nice to think about owning an air cooled model but I can't imagine what those museum pieces must cost to keep operational.

[clickman]

2001 base with 95,000 miles and original coil packs. By my math that makes them 20 years old. I bought a new set of Berus a few years back when I had a flashing CEL, but the problem went away and I never put them in. I wonder if I'll notice a difference if I install them...

[986 Boxster]

2001 2.7L with 134.000km (83k miles) still on the original coils. I never change coils on a car unless they give me problems. I know that a lot car manufacturers recommend changing coils at 100k miles, but I`ve never done it unless I get a code that they are bad. Of all the cars I`ve had, I`ve only had to change one coil on a car with 366k km (227k miles).

[jaykay]

never replaced

[Rob175]

All good to know, because my "indy" recommended mine get changed now at 90,000 miles even though the car runs just fine.

[Boxstard]

I thought the coil either works or doesn’t and when it doesn’t CEL gets triggered and you know it from the code. I got a 97 with 98K miles, with what appear to be original coils. One tube had split but just used electric tape for insulation. I don’t mind replacing them if aged coils affect engine performance appreciably but I’m not convinced if this is true,

I had a 2003 Saab for 16 years and put 170K miles on it, and its coil cartridge is considered a wear item, replaced it every 30K miles or so and carried a spare in trunk just in case. It went through several design revisions too so apparently some design flaws involved. You still gets CEL and code to know it’s gone.

So it’s case by case but it seems coils on 986 are designed well and robust.

[blue62]

Originally Posted by Boxstard

I thought the coil either works or doesn’t and when it doesn’t CEL gets triggered and you know it from the code. I got a 97 with 98K miles, with what appear to be original coils. One tube had split but just used electric tape for insulation. I don’t mind replacing them if aged coils affect engine performance appreciably but I’m not convinced if this is true,

I had a 2003 Saab for 16 years and put 170K miles on it, and its coil cartridge is considered a wear item, replaced it every 30K miles or so and carried a spare in trunk just in case. It went through several design revisions too so apparently some design flaws involved. You still gets CEL and code to know it’s gone.

So it’s case by case but it seems coils on 986 are designed well and robust.

Your assumptions are incorrect
Ignition coils can fail totally or they can exhibit intermittent failure.
They can also exhibit weak spark and never miss or fail.

Also there is no CEL (OBDII) code for ignition coils.
There are codes for misfires, but misfires can be caused by many factors not just coil issues.

[986 Boxster]

Originally Posted by blue62

Your assumptions are incorrect
Ignition coils can fail totally or they can exhibit intermittent failure.
They can also exhibit weak spark and never miss or fail.

Also there is no CEL (OBDII) code for ignition coils.
There are codes for misfires, but misfires can be caused by many factors not just coil issues.

Yes you're right, you don't get a code for a coil being bad, but you do get a code for a miss fire, and 99% of the time it's a bad plug or a bad coil. So it's very simple to figure out if you have a bad coil or a bad plug. Let's say you get a code for cylinder #4 for example, all you have to do is change a coil from a different cylinder to #4 and you will know if you have a bad coil or a bad plug. If the code comes back to cylinder #4 you know you have a bad plug, but if the code comes back to the cylinder that you changed the coil to, you know it's a bad coil

[blue62]

Originally Posted by 986 Boxster

Yes you're right, you don't get a code for a coil being bad, but you do get a code for a miss fire, and 99% of the time it's a bad plug or a bad coil. So it's very simple to figure out if you have a bad coil or a bad plug. Let's say you get a code for cylinder #4 for example, all you have to do is change a coil from a different cylinder to #4 and you will know if you have a bad coil or a bad plug. If the code comes back to cylinder #4 you know you have a bad plug, but if the code comes back to the cylinder that you changed the coil to, you know it's a bad coil

All true if you have a bad plug or bad coil.
You could also have a coil wiring issue on cylinder #4
You could also have a fuel injector issue or injector wiring issue on cylinder #4
Or valve train issues on cylinder #4 ect.ect.ect.
And get the same #4 cylinder misfire code.

My point to the OP was there is no CEL or OBDII codes that tell you a coil is faulty.

Misfire codes are triggered for many reasons depending on frequency and severity of the misfire.
The reason for the misfire as you pointed out has to be determined by diagnostics.

[Boxstard]

Originally Posted by blue62

All true if you have a bad plug or bad coil.
You could also have a coil wiring issue on cylinder #4
You could also have a fuel injector issue or injector wiring issue on cylinder #4
Or valve train issues on cylinder #4 ect.ect.ect.
And get the same #4 cylinder misfire code.

My point to the OP was there is no CEL or OBDII codes that tell you a coil is faulty.

Misfire codes are triggered for many reasons depending on frequency and severity of the misfire.
The reason for the misfire as you pointed out has to be determined by diagnostics.

OK I stand corrected but coil failure is still easily diagnosed with the CEL code for misfiring. Intermittent failure/ misfiring can be felt, if it does not trigger CEL. Ilm still skeptical if ‘weak’ spark from an aged coil can appreciably reduce engine power, and if so what characteristics one can check on a coil and justify replacement.

[blue62]

Originally Posted by Boxstard

OK I stand corrected but coil failure is still easily diagnosed with the CEL code for misfiring. Intermittent failure/ misfiring can be felt, if it does not trigger CEL. Ilm still skeptical if ‘weak’ spark from an aged coil can appreciably reduce engine power, and if so what characteristics one can check on a coil and justify replacement.

Start with a visual inspection.
I always use a flashlight.
If they have any type of physical damage like cracks in the housing (even hairline cracks) I replace them.

A simple test you can do on a coil yourself is an Ohm's resistance test.
If a coil doesn't meet manufactures spec. it should be replaced.
You can usually find the manufactures spec on the internet.
All you need for the test is a Digital multi meter.
If you do your own auto work you should have a Digital multi meter in your tool box.

[DrRobin]

Thanks everyone, that is quite a spread of miles out of a set of coils and it looks like mine are typical.

When the dealer changed mine from original to Beru 10 years and 40k miles ago I did notice a difference, the engine ran smoother. There was no misfire or CEL.

When I have just changed them now, all six had at least one small crack, but the difference isn't quite as noticeable, it is running a lot better, but was after stripping out one side and cleaning the coils/plugs. I did test the coils with a meter, the values for resistance were within spec.

I did get a CEL a couple of months ago, but that was when the battery was quite weak, so in my experience to answer a couple of questions posed here:

- If you have a weak spark, you might not get a misfire or CEL, but you will get poor burning of the fuel and it will lead to rough/poor running.

- Cleaning all the crud off the coils and the plugs will always help.

- If the coil has cracks in it then it will start to break down, especially when wet and this will produce a weak spark/CEL.

- I got Beru coils in the UK for £31 each, at that price it isn't worth fitting anything else. I also got 6 Denso original fitment spark plugs for about £28, again not worth cleaning the old ones which looked fine to me.

So for about £210 (and a couple of afternoons) I have new coils, new plugs, the old plugs didn't show anything out of the ordinary so I am happy that my 986 at 93k miles is good for another few miles.

[Boxstard]

Originally Posted by blue62

Start with a visual inspection.
I always use a flashlight.
If they have any type of physical damage like cracks in the housing (even hairline cracks) I replace them.

A simple test you can do on a coil yourself is an Ohm's resistance test.
If a coil doesn't meet manufactures spec. it should be replaced.
You can usually find the manufactures spec on the internet.
All you need for the test is a Digital multi meter.
If you do your own auto work you should have a Digital multi meter in your tool box.

Yeah that’s pretty basic…. For me cracking can be repaired and may not warrant automatic replacement, if you catch it early. Body crack can be filled with epoxy, and tube can be insulated with electric tape. One of mine had tube split and taping it up works fine.

I do have a multimeter, but just wondering how to tell actual degradation, instead of just continuity of the coil. Variation in reading within the spec. may come from manufacturing tolerance, instead of aging. If the coils with resistance within the spec. can still produce weak spark, then the check is not effective and I wonder what else can be checked.

[DrRobin]

Originally Posted by Boxstard

Yeah that’s pretty basic…. For me cracking can be repaired and may not warrant automatic replacement, if you catch it early. Body crack can be filled with epoxy, and tube can be insulated with electric tape. One of mine had tube split and taping it up works fine.

I do have a multimeter, but just wondering how to tell actual degradation, instead of just continuity of the coil. Variation in reading within the spec. may come from manufacturing tolerance, instead of aging. If the coils with resistance within the spec. can still produce weak spark, then the check is not effective and I wonder what else can be checked.

When you measure the resistance to be less than 0.7 ohms, that is just the primary coil and my guess would be that it is the secondary which is more important. You can measure the secondary resistance, but a better measurement would be the insultation resistance, for which I haven't seen any figures.

If the insulation has cracked, unless you get all of the moisture out before it is sealed with epoxy you will still compromise the insulation resistance and therefore might end up with a weak spark. I would only do this as a short term fix until new coils can be obtained.

It took me 3 hours to change all six coils/plugs and coils were £31 each in the UK, I doubt it is really worth the effort of removing a coil, drying it out, filling with epoxy and re-fitting, well not in our current autumn climate of cold temperatures and rain.

If you were a little closer, you could have 6 Beru coils, all with at least one crack, but the postage would be more than they are worth.

PS anyone in the UK is welcome to them if they pay the cost of posting from Northumberland.

[blue62]

Originally Posted by Boxstard

Yeah that’s pretty basic…. For me cracking can be repaired and may not warrant automatic replacement, if you catch it early. Body crack can be filled with epoxy, and tube can be insulated with electric tape. One of mine had tube split and taping it up works fine.

I do have a multimeter, but just wondering how to tell actual degradation, instead of just continuity of the coil. Variation in reading within the spec. may come from manufacturing tolerance, instead of aging. If the coils with resistance within the spec. can still produce weak spark, then the check is not effective and I wonder what else can be checked.

Continuity and Ohm's resistance are not the same thing.
They are two different tests.
If you have a variation in reading "within the spec." your still within spec.
Any spec. has an allowable tolerance.
Primary and secondary Ohm's resistance can be checked with a Multimeter.
Spark color can be checked with a simple spark checker.
You want a fat blue spark not a weak yellow spark.
You can do a cylinder power balance test to see if a coil is possibly having a negative power balance effect on the engine.
You can have the coils scoped.

But in my opinion at less then $50.00 apiece shipped to my front door. If I have doubts about the condition of a coil I replace them.
Anything else is penny wise and pound foolish.