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Old 08-22-2017, 02:41 PM   #1
equ
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Replace one ignition coil or all six?

On the 535i a CEL that keeps coming back (and this time here to stay) seems to be due to a weakening coil (car still gets 27mpg) highway. Perhaps this coil is the reason for a shaky idle. I'm not sure.

Shop called me. If I replace one coil, it's $180 with labor. Should I replace all six for $580 (with labor) preemptively?

Plugs were done 10k miles ago.
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Old 08-22-2017, 02:46 PM   #2
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If I solve the basic algebra, that means they are charging $100 for labor (same for one or all six) and $80/coil. ECS has the BMW coils for $60 each. The mark-up is reasonable (and I don't have gear to check/clear CEL's and what not). I'm sure it's not a hard job.

Then again, they had a pretty decent price on the brake jobs (which is what the car is in for). Car is at 50k miles.
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Old 08-22-2017, 02:52 PM   #3
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If your 5 is anything like an E46, you should DIY.

Pretty easy really.
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Old 08-22-2017, 02:58 PM   #4
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True. But it's at the shop and they're generally a reasonable bunch. And if it continues to miss at idle, I can hold it over them.Get them to check the plug gaps etc (stuff I can't do).
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Old 08-22-2017, 03:03 PM   #5
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Quote:
Originally Posted by equ View Post
If I solve the basic algebra, that means they are charging $100 for labor (same for one or all six) and $80/coil. ECS has the BMW coils for $60 each. The mark-up is reasonable (and I don't have gear to check/clear CEL's and what not). I'm sure it's not a hard job.

Then again, they had a pretty decent price on the brake jobs (which is what the car is in for). Car is at 50k miles.
I'd probably just do them all. Chances are if one is at EOL the remaining 5 are pretty close.
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Old 08-22-2017, 03:04 PM   #6
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Originally Posted by 3LOU5 View Post
If your 5 is anything like an E46, you should DIY.

Pretty easy really.
This. It's like 3 small bolts.
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Old 08-22-2017, 03:06 PM   #7
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Lou: Seems unethical for me to complain about CEL & idle to the shop, they trace it to a coil and then I say, ok, I'll DIY it.

One solution would be to have them do the one and I do the five at home.

I think I'm just going to have them do it. This car has not been too expensive to buy or run.
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Old 08-22-2017, 03:16 PM   #8
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I'd probably just do them all. Chances are if one is at EOL the remaining 5 are pretty close.
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Old 08-22-2017, 03:31 PM   #9
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I can't speak to the actual mechanic, just the guy on the phone. So I'm not sure if they "tested" that coil to be bad or just going of the CEL and the mechanic has a hunch (and he's been pretty ok).

Anyway, they are reasonable. I've been driving like this for 7k miles, I think I can weather another week or two. Turns out they were selling a $40 (ECS Tuning price) delphi coil at $80 to me, but they are also ok if I bring my own parts. I'll either do that or I'll DIY it. Might be harder on the n55 turbo compared to the m52/m54 series - strut bars may have to come off.
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Old 08-22-2017, 03:57 PM   #10
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They should charge you a diagnostic fee. I wouldn't feel bad about paying for the diagnosis and doing the work myself.

I have no idea how they identified a coil getting "weak." If they scanned the car and saw a misfire on one cylinder, that would indicate (likely) that the specific coil had failed. If it were my car, I'd replace all the coils at that point.
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