[WhiteFury]

When I first start up The car everything is fine and as it starts to warm up and the RPMs drop to around 1000 the idle slightly surges up-and-down about 100 RPM it's very slow and faint.

Even if the car is completely warm and I turn the car off for 10 or 15 minutes when I start it back up it does the same thing after however after two or three minutes it completely goes away.

Any thoughts on what this is? I also wanted to seafoam to clean out some of the intake manifold however I don't know what vacuum line to use since I don't have any lines like the N54 engine does.

Any thoughts? Thanks!

[WhiteFury]

Also just realized my exhaust on the driver side has a throttle flap that is always open.

[nikkisc]

this happens to me too, it usually stops once I make sure the a/c is off. I brought it in for service but my advisor said that it's normal for the n55s. he said he reset something with the idle but it still happens.

[ashmostro]

Idle air control system when cold... normal, particularly if it goes away after the car runs for a bit.

[WhiteFury]

It will do it even if I shut the car off for 5-10 min and start it back up while its still warm. So this is normal?

[SRT14PimPin07]

http://www.e90post.com/forums/showthread.php?t=798567

I don't know if this applies to you, but sorta the same thread I had made a while ago. Maybe it can help.

[BavarianBullet]

Cars have been doing this since the advent of computerized engine control in the 80s. It's poor programming in the ECU/DME that causes the idle to cycle up and down. The DME is literally seeing an unplanned drop in idle RPM, opens the throttle to correct it, overcompensates slightly, backs the throttle down again and just keeps looping like this until the condition clears.

Lots of things can cause it to happen with the usual suspect being EGR (clogs, bad valves or sensors), esp on cars with more mileage on them.

In the N55's case, in my own experience, it seems to be related to turning on the climate controls (A/C typically) in the first minute or so when the car starts up from cold. This puts more load on the engine and drags down the idle RPM and then the above DME looping begins. I'd highly suggest the TSB for the ECU update suggested earlier. I'd be surprised if it didn't fix it.

[WhiteFury]

There's a free ecu update from BMW?

[boostd92]

^^There is a TSB regarding this issue. Your car has to fall within the build dates, but the specific text regards surging idle at load or cold starts. It's been updated several times as well, the fix is a software update. SIB 12 09 12.

If your software version is newer than March 2013, it doesn't apply, or if your car is newer than March of 2012.

[WhiteFury]

Originally Posted by boostd92

^^There is a TSB regarding this issue. Your car has to fall within the build dates, but the specific text regards surging idle at load or cold starts. It's been updated several times as well, the fix is a software update. SIB 12 09 12.

If your software version is newer than March 2013, it doesn't apply, or if your car is newer than March of 2012.

This is what my paper for the tsb at the dealer says. He said I have to pay for it since i have 63k miles.

[WhiteFury]

Also dealer said it may decrease performance which makes no sense. Can anyone vouch that it doesn't make the tune more conservative?

Also when I let off the brake pedal and let the car start to coast, if I turn the wheel sharp left or right the idle jumped and car moves faster without even touching the gas. Is this norm for these cars?