[Tepr05]

I'm a new owner of a 2011 335 and am experiencing idle surging upon cold start. I took it to the dealer and they basically said its throwing no codes so its not a problem and it's "normal" for this to happen especially because it's only temporary (first 20 seconds or so after start). I noticed at first that it seemed to only occur when the AC compressor kicked on right away however its doing it now with the AC off and just about with every cold start. I found a few threads on similar issues but wanted bring some attention to see if anyone has experienced this exact issue with an N55. Check out the video:

[BMV///M3]

I'd say def not normal. N54 here but mine does an initial idle spike like the vid at the 10 sec mark, however it DOES NOT continue like that one.

Carbon build up? Hard to imagine on a 2011 though. Maybe slight injector issue?

[bman5150]

My 2011 335xi also does the same thing. If I stab the throttle, it seems to settle down. Also, I don't think mine does it unless the ac is on. If I manually turn off the ac before I turn the car off, it doesn't seem to idle erratically when I go to restart it later.

Is not normal but I've yet to encounter a serious problem as a result. Wonder if its just a software issue?

[Tepr05]

Originally Posted by BV335

I'd say def not normal. N54 here but mine does an initial idle spike like the vid at the 10 sec mark, however it DOES NOT continue like that one.

Carbon build up? Hard to imagine on a 2011 though. Maybe slight injector issue?

Carbon build up now that you mention it could be a culprit. I've had the car about a month and all of my driving is short distances (<10 miles typically). Poor thing barely gets its oil warm most trips. That would also explain the increase in frequency I've seen over the last week.

[fazman]

Definitely not normal for any vehicle. I just came from the BMW HQ event they had about a week ago. This not anywhere near the, "We have an obsession for perfection in minor details for our luxury owners..". Surging/bouncing idle on startup is NOT obsession for a great BMW experience when I start "my" car in the early morning. It's definitely NOT the way "I" would want to start my morning when I get into the "Ultimate Driving Machine".

Just spit some of that back at your SA, then walk out and start going to a new BMW service location. Your car on a cold start up should idle high for a moment (about 1500 rpm-ish) and then gradually taper down to a rock solid 750 RPM. I would estimate about 2 or 3 seconds per 100 RPM drop (ball parking here)... but you get the idea that it is a linear diminishing RPM from the initial start up spike. Never should it bump upwards... only downwards towards the target RPM of 750.

The reason you get the spike on cold start is because the ECU doesn't want the car to stall out... once its running it gradually moves towards it's target RPM in a closed loop. If your bouncing the RPM's... that is only going to happen if you have a faulty Throttle Position Sensor, you are tapping on the gas peddle, or vacuum leaks it's compensating for. Next question is.... after a few minutes the car should switch to open loop... wondering if you are having any idle issues then?

[williamf]

I think there are also emission requirements for the "normal" RPM spike at startup. The catalyst needs to warm up quickly in order to keep the Nox emissions within federal guidelines. At least this is what I have been told.

I suspect that if you could get a reading on cylinder misfires, you would find that the first couple of minutes you have a ton of misfires. These are dealt with by the ECU adjusting timing, fuel and other engine parameters. If I am right, though this is annoying, it will not damage the car.

I agree 100% that the Ultimate Driving Machine should be smooth from the moment you crank the engine. If a Honda civic can run smooth for 200K, then it is not too much to ask for a BMW to run smoothly for 50K to 100K miles.

[CJ421]

Absolutely not normal. Something is wrong, no idea what. I have a 2011 N55 and it does what others have said - goes to maybe 1100 at first, then settles to just below 1000 for 10 secs then 750rpm idle, stable.

[Titanium3er]

I have an N54, but this looks very similar to issues I was having recently. My idle surge was not nearly as pronounced as yours, but I also had symptoms while in motion that almost felt like a transmission knock.

To make a long story short the first dealer said it was "normal". After giving them a piece of my mind, I brought to another dealer and they replaced spark plugs and coils. Issues got better, but didn't go away completely so I brought it back to them and they replaced the injectors and did carbon blast. That did the trick.

Keep on them until they fix this. If they give you a hard time tell them to get the regional field engineer involved. That's what mine did to get approval for the carbon blast under CPO warranty.

[Tepr05]

Originally Posted by fazman

Definitely not normal for any vehicle. I just came from the BMW HQ event they had about a week ago. This not anywhere near the, "We have an obsession for perfection in minor details for our luxury owners..". Surging/bouncing idle on startup is NOT obsession for a great BMW experience when I start "my" car in the early morning. It's definitely NOT the way "I" would want to start my morning when I get into the "Ultimate Driving Machine".

Just spit some of that back at your SA, then walk out and start going to a new BMW service location. Your car on a cold start up should idle high for a moment (about 1500 rpm-ish) and then gradually taper down to a rock solid 750 RPM. I would estimate about 2 or 3 seconds per 100 RPM drop (ball parking here)... but you get the idea that it is a linear diminishing RPM from the initial start up spike. Never should it bump upwards... only downwards towards the target RPM of 750.

The reason you get the spike on cold start is because the ECU doesn't want the car to stall out... once its running it gradually moves towards it's target RPM in a closed loop. If your bouncing the RPM's... that is only going to happen if you have a faulty Throttle Position Sensor, you are tapping on the gas peddle, or vacuum leaks it's compensating for. Next question is.... after a few minutes the car should switch to open loop... wondering if you are having any idle issues then?

When I don't have the idle surge it behaves exactly like you described. A few minutes after the surging, it doesn't appear to have any idle issues. I'll get a knock or two (feels like a misfire) sporadically at a stop light but nothing that seems regular, frequent or directly related to the surging.

[tpcon]

I have a 2011 335i and mine does this very rarely. but when it does happen it only spikes up once, maybe twice so definitely not as many times as yours

[Surly73]

Originally Posted by williamf

I think there are also emission requirements for the "normal" RPM spike at startup. The catalyst needs to warm up quickly in order to keep the Nox emissions within federal guidelines. At least this is what I have been told.

You're bang on.

Earlier BMWs (like my E39) and other German vehicles have used a secondary air pump to meet the same requirement. If you don't have the pump, then the engine is usually programmed to have a faster idle and run with retarded timing to send burning fuel straight into the cats to light them off.

My E39 would start and settle right to 600rpm from dead cold, but with the secondary pump running for anywhere from 10-90 seconds depending on ambient/engine temperature.

[Shon]

I had the same issue. Dealer replaced low pressure fuel sensor first, then fuel pump and problem went away.

[Dozhdbog]

Mine will surge over and over for maybe 20 seconds then drop to 750. This happens maybe once every other week or so. Sometimes I will also get a lurching start from a red light, most of the time not. I can't figure out what the hell is going on, but it's uncommon enough that I have been putting off making an appointment at the dealership.

[Meeni]

Originally Posted by Surly73

You're bang on.

Earlier BMWs (like my E39) and other German vehicles have used a secondary air pump to meet the same requirement. If you don't have the pump, then the engine is usually programmed to have a faster idle and run with retarded timing to send burning fuel straight into the cats to light them off.

My E39 would start and settle right to 600rpm from dead cold, but with the secondary pump running for anywhere from 10-90 seconds depending on ambient/engine temperature.

Interesting. I think you connected the dots for my own problems. I have a strange inconclusive reading from post-cat O2, and bouncy idle with warm engine, w/o misfire. Up to now I was confused (and since it is overall harmless, just got used to it), but now that makes sense...

[Surly73]

Originally Posted by Meeni

Interesting. I think you connected the dots for my own problems. I have a strange inconclusive reading from post-cat O2, and bouncy idle with warm engine, w/o misfire. Up to now I was confused (and since it is overall harmless, just got used to it), but now that makes sense...

I remember when I first heard about Valvetronic before it was released in production. My first thought was something like this - 'wow, those are going to be really tight valve tolerances - able to control IDLE with just the valves? I wonder how North America's crappy gas and bare minimum maintenance habits are going to play with that engine... I bet people are going to have all kinds of idling and other problems as the engines age.'

And, almost 10 years later, here we are. Everyone and their brother has some kind of rough idle, bouncy idle, sputtering, "not like it used to be" etc... Honestly I'm not surprised at all. But, I find myself owning one of these engines. Valvetronic leads to a bunch of technical and performance advantages but smooth idle sure isn't one of them.