Replacing Ignition Coils Preventatively?

[blaelock]

Forgive me if this has been covered, but I couldn't find an answer to my specific question. In my quest to preventatively maintain my S4, I'm wanting to replace my spark plugs and potentially my coils. My spark plugs have been replaced twice during my car's life in 40,000 mile intervals. I'm approaching 40k miles on my current set of plugs so I think it's time. My question is simple; although all 8 of my coils were replaced under the recall a few years ago, should I still consider replacing them with my plugs or should I simply reuse them and not worry?

[Slow4]

Are you having misfires or rough idling?

If not, save the money and replace the plugs. If you really want, have a few coils on standby.

[dparm]

Waste of money. Coils have an incredibly long life span.

Also, why are you replacing plugs so often? Are you running an ultra-sharp tip that wears down quickly?

[blaelock]

Waste of money. Coils have an incredibly long life span.

Also, why are you replacing plugs so often? Are you running an ultra-sharp tip that wears down quickly?

I was following the original owner's service interval for the plugs, which I calculated to be around 40,000 miles. I also did some research on the topic and I believe I read about others following the 40,000 mile interval - I'll have to see if I can find where I read that. I did find this to be a bit often because on my previous BMWs I had followed a 100,000 mile interval. How often should I be replacing them? I recently had a leaking valve seal issue dealt with, so my current set of plugs was getting loaded with oil for some time. Would that be a reason to consider replacing them?

Just for note, only original Genuine Audi/Bosch units have been used.

Are you having misfires or rough idling?

If not, save the money and replace the plugs. If you really want, have a few coils on standby.

No misfires or rough idling. Thank you for the input.

[dparm]

IIRC the S4's plug change interval is 100k. Most opt for 50k, but from all the photos I've seen posted, even that is probably too early. I swapped mine at 50k and they looked just fine (gap was still pretty close).

A quad-tip platinum plug can easily handle a 50k interval.

[blaelock]

Here's a shot of one of my driver's side front plugs during my oil consumption problem which has since been remedied. These plugs have around 38,000 miles on them.

[brndll]

They (coilpacks) do last a long time. I can say categorically that coils will last 100K... well almost 100K. I just did my coilpack recall last week and I am at 97K. The recall limit is 100K so just under the wire by the way, thank you, thank you. I changed the plugs at around 50K just because (also put a new set in a few days before they did the recall service). I never had any issue with misfires or rouch idle until last week, which precipitated the order of new plugs, then coil "move around and follow misfire" test, and ultimately a trip to the dealer service dept.

[WolfS4]

FWIW, I had a dealer installed, post recall coil pack fail on me after ~50k miles.

http://www.audizine.com/forum/showth...l-pack-failure

I plan on replacing all of them when I find time.

[dparm]

Here's a shot of one of my driver's side front plugs during my oil consumption problem which has since been remedied. These plugs have around 38,000 miles on them.

Yes, a plug that was fouled by oil consumption will need to be replaced. But a healthy engine doesn't need new plugs every year.

[blaelock]

Thank you for the input everyone. In light of what I've learned in this thread, I'm planning on replacing my fouled plugs with Bosch replacements and reusing my coils since they've already been replaced once.

WolfS4, I've never seen a coil fail like that. As with everything on my car, I'll keep a close eye on them but that is quite surprising!

[elwigglero]

I replaced plugs at 50k miles and the difference was night and day - gained quite a bit of lost power. I burn very little oil - all were clean (relatively), but simply worn to hell. Luckily, they're pretty easy to check, so pull your coilpacks and check the plugs out when you have a few minutes. Plugs are a maintenance item on this car (others have different experiences, but I plan to replace mine every 30-40k miles) and aren't prohibitively expensive.

Coilpacks have a way of letting you know when they need to be replaced - rough idle, intermittent misfires on random cylinders, etc. Don't replace them unless you have symptoms to justify the cost.

[mbgt72]

If you're a B6 S4, you're probably within the coilpack recall and could get new coilpacks free through the dealer. I was an 05.5 and missed it by only a couple letters, but I believe some 05.5 have received free coilpacks.

I believe "Q" is the cutoff letter for whether coilpacks fall under the recall or not. You can pull the harness off of one bank and look at the part number to determine if it is a valid recall part number or not.

[blaelock]

Luckily, they're pretty easy to check, so pull your coilpacks and check the plugs out when you have a few minutes.

Coilpacks have a way of letting you know when they need to be replaced - rough idle, intermittent misfires on random cylinders, etc. Don't replace them unless you have symptoms to justify the cost.

I uploaded a photo in this thread and in another one. You can see it above. The plugs are fouled from an leaking valve seals which have since been replaced. Even though my plugs have only 38k on them I'm going to replace them and then decide on an interval somewhere between 50-75k after that. My coils aren't causing any misfires or other issues so I'm thinking they're okay for the time being.

If you're a B6 S4, you're probably within the coilpack recall and could get new coilpacks free through the dealer. I was an 05.5 and missed it by only a couple letters, but I believe some 05.5 have received free coilpacks.

I believe "Q" is the cutoff letter for whether coilpacks fall under the recall or not. You can pull the harness off of one bank and look at the part number to determine if it is a valid recall part number or not.

My coil packs were replaced under the recall by Audi a few years ago.

[brndll]

I was told by my dealer that the cutoff is 100K if you have not done the recall.