[Hydro]

Every once in a while while sitting at a red light, or parking lot, or my garage etc. my engine RPM's will start to fall close to 500. It feels like it's about to stall, and then it goes back up to normal idle RPM. Any idea what is causing this?

[e92_enthusiast_1]

Does it happen all the time or only like when you first take off in the morning (i.e when the engine's still not up to temp)?

It could be a few things though if its not just normal rpm fluctuation:

a) plug(s) going
b) coil(s) going
c) intake carbon buildup

w/o codes though its hard to tell. Have you changed or done a, b, or c recently?

[Hydro]

Originally Posted by e92_enthusiast_1

Does it happen all the time or only like when you first take off in the morning (i.e when the engine's still not up to temp)?

It could be a few things though if its not just normal rpm fluctuation:

a) plug(s) going
b) coil(s) going
c) intake carbon buildup

w/o codes though its hard to tell. Have you changed or done a, b, or c recently?

I'm not sure... I just bought the car last month. How can I find out?

[e92_enthusiast_1]

In general plugs and coils are not recommended maintenance on the DI motors until like 50k miles (n54) they use to say it was 100k (still true for n52 NA) miles but that was revised but not sure which month/year . As another example BMW recommends every 35k or so miles for their performance M line. I'm at 31k miles on mine and im getting everything to do it soon, will prolly swap them out around 35k-40k miles.

Carbon intake cleaning there's no way to tell unless you remove your valve cover and inspect the intakes.

My guess it's never been done.. People normally wont do it because its fucking expensive if you do it at the stealership and it's not part of the warranty.

Originally Posted by Hydro

I'm not sure... I just bought the car last month. How can I find out?

[Hydro]

Originally Posted by e92_enthusiast_1

In general plugs and coils are not recommended maintenance on the DI motors until like 50k miles. That's just BMW's recommendation though.

Carbon intake cleaning there's no way to tell unless you remove your valve cover and inspect the intakes.

My guess it's never been done.. People normally wont do it because its fucking expensive if you do it at the stealership and it's not part of the warranty.

Ya, I've been quoted at ~$500 for intake cleaning.

How much are the plugs and coils if I change them myself? Where can I buy them?

[e92_enthusiast_1]

I'm going with one of the ecstuning kits.

Bosch Brand Ignition Kit $329.95

or

OEM BMW Ignition Kit $418.62

You don't HAVE to do coils too but once i'm in there I just like doing it all at once. Fresh coils and plugs for my baby girl
The coils are def more expensive so if you're strapped you could start just with the plugs and it would be much cheaper.

Originally Posted by Hydro

Ya, I've been quoted at ~$500 for intake cleaning.

How much are the plugs and coils if I change them myself? Where can I buy them?

[Hydro]

Is there any way to tell if your plugs are the only thing that needs to be changed? Or is it just a general rule of thumb that they go out at the same time.

Originally Posted by e92_enthusiast_1

I'm going with one of the ecstuning kits.

Bosch Brand Ignition Kit $329.95

or

OEM BMW Ignition Kit $418.62

You don't HAVE to do coils too but once i'm in there I just like doing it all at once. Fresh coils and plugs for my baby girl
The coils are def more expensive so if you're strapped you could start just with the plugs and it would be much cheaper.

[e92_enthusiast_1]

No rules of thumb for them going out at the same time and I don't have a good way of telling a coil is bad. They're basically good until they go bad and at that point you're throwing codes for misfires usually.

Just call up your dealer and ask them, "Hey, when's the last time the coils/plugs were changed?"

Hopefully, there's a good history and they can tell you.

Depending on what they say give it a bit and see if maybe it's just really just a random anomaly.

Originally Posted by Hydro

Is there any way to tell if your plugs are the only thing that needs to be changed? Or is it just a general rule of thumb that they go out at the same time.

[Hydro]

Alright. I'll do that. My guess is that it is the intakes. Thanks for your help.

Out of curiosity, did you have your chrome trim painted or vinyl wrapped? It looks really good.

Originally Posted by e92_enthusiast_1

No rules of thumb for them going out at the same time and I don't have a good way of telling a coil is bad. They're basically good until they go bad and at that point you're throwing codes for misfires usually.

Just call up your dealer and ask them, "Hey, when's the last time the coils/plugs were changed?"

Hopefully, there's a good history and they can tell you.

Depending on what they say give it a bit and see if maybe it's just really just a random anomaly.

[e92_enthusiast_1]

Shadowline gloss/matte factory option actually. I got her 2 wks ago and I though it was vinyl wrapped too but then I checked my VIN and realized that's a factory option it had. I think it looks 100x better than chrome too and I believe mines gloss not matte.

Originally Posted by Hydro

Alright. I'll do that. My guess is that it is the intakes. Thanks for your help.

Out of curiosity, did you have your chrome trim painted or vinyl wrapped? It looks really good.

[Hydro]

Originally Posted by e92_enthusiast_1

Shadowline gloss/matte factory option actually. I got her 2 wks ago and I though it was vinyl wrapped too but then I checked my VIN and realized that's a factory option it had. I think it looks 100x better than chrome too and I believe mines gloss not matte.

Well it looks really good. I can't decide if I want mine Gloss or Matte. With a Monaco blue car, too much black can begin to look cheap IMO. But the chrome annoys me.

[Bluesnake01]

More than likely carbon build up. Mine does it at times. My spark plugs have less than 10k miles and just recently got my injectors changed from the dealer thru a recall. I would recommend checking that out as well, there was a recall from late MY07 modesl thru mid? MY09.

Im gonna get mine cleaned up soon before it actually starts to become a problem. Aside from idle, I dont feel any loss of power or hiccups during WOT or normal driving.

[chepy24]

i see my car doing this and at times. it has shook from side to side like king kong is in the trunk trying to get out...only has happened twice the first time scared the crap out of me no codes or anything and only when it was about -9 here in denver

[michaelalex17]

do you run with the A/C on or off? Turn it on and your rpm's will run slightly higher

[Hydro]

Originally Posted by chepy24

i see my car doing this and at times. it has shook from side to side like king kong is in the trunk trying to get out...only has happened twice the first time scared the crap out of me no codes or anything and only when it was about -9 here in denver

This made me laugh. It's a pretty good way to describe what happens hahahaha.

[Hydro]

Originally Posted by Bluesnake01

More than likely carbon build up. Mine does it at times. My spark plugs have less than 10k miles and just recently got my injectors changed from the dealer thru a recall. I would recommend checking that out as well, there was a recall from late MY07 modesl thru mid? MY09.

Im gonna get mine cleaned up soon before it actually starts to become a problem. Aside from idle, I dont feel any loss of power or hiccups during WOT or normal driving.

How do I find out what the recalls for my car are and if they've been fixed?

[Bluesnake01]

Originally Posted by Hydro

How do I find out what the recalls for my car are and if they've been fixed?

Best bet is to call a local BMW dealer and ask them if they can check the vin to see if they had done any recalls on the injectors.

I believe they have to pull every injector and check the SN's to see if they need to change them or not. See attachments.