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Discussion Starter · #1 ·
Getting ready to install new plugs in my '05 325Ci. Should I be thinking about coil packs too? I bought the car 2 years ago this week, and it's been running smooth as silk until about a month ago, when I started sensing that there just might be a touch of a miss when I start it from cold. No audible sound, and the sensation disappears by the time I get to the end of the driveway. Did the injectors when I replaced the CCV back in December, so no suspects there.

Anything else I need to be looking out for?

Thanks in advance!
 

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That's hard to diagnose over the internet. First thing that comes to mind is a leaky injector that caused a bit of fuel to dribble down into one of the cylidners or something. Replacing the injectors doesn't really mean anything anyway. they're usually used and the quality may come down to the person servicing and/or installing them.

Why did you replace them to begin with? it's sort of an oddball part to replace.
 

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'02 330i 5-Speed
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Coils can be intermittently bad. I had a bad coil that would only manifest under certain conditions. Rest of the time it ran perfectly smooth. One of the times would be if I hadn't driven the car in a couple of days and started it from cold, it felt like it was running on 5 cylinders until the coil "woke up."

Any codes?
 

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To give some real-world data without any proven accuracy...
Coils on my 04 330 had about ~150,000mi in them before one went bad.
--At that point I pulled them and replaced all six with Delphi coils from FCP

Now I have 5 spares.

When I pulled them I found they were Bosch and likely either original or replaced on a campaign within the first ~5 years of life.

Estimating 100 - 150k of useful life before they start looking 'burnt' Ill take a pic when i get home if you'd like.
 

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2001 325ci
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Getting ready to install new plugs in my '05 325Ci. Should I be thinking about coil packs too? I bought the car 2 years ago this week, and it's been running smooth as silk until about a month ago, when I started sensing that there just might be a touch of a miss when I start it from cold. No audible sound, and the sensation disappears by the time I get to the end of the driveway. Did the injectors when I replaced the CCV back in December, so no suspects there.

Anything else I need to be looking out for?

Thanks in advance!
2001 325ci
320xxx miles
original ignition coil set
replaced spark plug set once (with ccv), I have a set standing by. got to do soon.
replaced 2 ignition coil booths (with ccv)

so if you're replacing spark plugs, at least inspect coil booths for cracks
 

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The coils could be a crap shoot. I had one go bad on my '03 not long after I bought it brand new. The dealer replaced it under warranty. A few months later 2 more died and the dealer replaced the entire set. Both times the ECM threw misfire codes. Now at 250k miles or so and they are still going strong.
 

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Discussion Starter · #11 ·
That's hard to diagnose over the internet. First thing that comes to mind is a leaky injector that caused a bit of fuel to dribble down into one of the cylidners or something. Replacing the injectors doesn't really mean anything anyway. they're usually used and the quality may come down to the person servicing and/or installing them.

Why did you replace them to begin with? it's sort of an oddball part to replace.
Hi, Mango- thanks for the input!
I realize I wasn't very clear with "did the injectors". What I did was to give them a through cleaning while I had the manifold off doing a CCV replacement.
 

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Discussion Starter · #13 ·
To give some real-world data without any proven accuracy...
Coils on my 04 330 had about ~150,000mi in them before one went bad.
--At that point I pulled them and replaced all six with Delphi coils from FCP

Now I have 5 spares.

When I pulled them I found they were Bosch and likely either original or replaced on a campaign within the first ~5 years of life.

Estimating 100 - 150k of useful life before they start looking 'burnt' Ill take a pic when i get home if you'd like.
I got around to changing plugs this afternoon- All 6 looked identical, just a light grey color. The coil connections had a bit of light brown, but that was all. When I started the car, the problem seemed to be gone.
 

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Discussion Starter · #14 ·
2001 325ci
320xxx miles
original ignition coil set
replaced spark plug set once (with ccv), I have a set standing by. got to do soon.
replaced 2 ignition coil booths (with ccv)

so if you're replacing spark plugs, at least inspect coil booths for cracks
Nice to hear of an m54 with that many miles! Have you had to do any work on it? Changed plugs today, checked, didn't find any cracks.
 

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Discussion Starter · #16 ·
The coils could be a crap shoot. I had one go bad on my '03 not long after I bought it brand new. The dealer replaced it under warranty. A few months later 2 more died and the dealer replaced the entire set. Both times the ECM threw misfire codes. Now at 250k miles or so and they are still going strong.
So I changed the plugs today and inspected the coils. No sign of damage. But the plugs had "Bosch BMW" printed on them. I wonder if those were the originals? Car has 170k miles on it.
 

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Discussion Starter · #17 ·
Coils can be intermittently bad. I had a bad coil that would only manifest under certain conditions. Rest of the time it ran perfectly smooth. One of the times would be if I hadn't driven the car in a couple of days and started it from cold, it felt like it was running on 5 cylinders until the coil "woke up."

Any codes?
That's interesting it would behave that way. Did the plugs today, inspected the coils. Plugs were all identically grey, with no signs of chipping or pitting. Coils had no cracks, and peering down the tube to the connector, I saw only a light brown color. Once the job was done, the problem seems to have gone away.
 

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Coils have easy to spot date codes. From my casual survey at the boneyard, most coils are original.

I've never had to change a coil, but I've had to change several connector boots. Boots cost about the same as spark plugs, and I've come to think that they should be replaced on the same schedule. They will still look OK at 100K miles, but by 200K they have a good chance of missing the lip or splitting when you squeeze them.
 

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I changed original coils at around 140k miles. One by one I've been putting the originals back in as the new ones failed quickly over the next 70k miles and 6 years. 2 of the new ones failed within 2 years. Not impressed.
 

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Coil packs can be hit or miss (if defective), but for the most part they have a very long service life.

My original coil packs have 200K miles on them. As a point of contrast, my friend's M240i had a coil pack fail shortly after getting the car (within 5K miles).

They aren't expensive for the M54 and my plan is simply to replace the lot if/when the first 1-2 fail.
 
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