[fedinand]

I know there was a thread about the RPMs jumping/fluctuating on some start-ups. Our X3 is doing it pretty consistently, but is also stops about 10 - 15 seconds in. I realized I caught it on video when I was looking at an old vid. You can hear the rpms going up and down in the very beginning, and it stops and gets steady right around 16 - 17 seconds into the vid. Can those of you who said their X3s did this chime in and let me know if this is what your X3's sound like when your RPMs jump upon start up?

[Lotus7]

Mine will fluctuate idle speed from 1000 to 1400 rpm for about 15 seconds after a cold start up only if the air conditioner is on (presenting an additional load to the engine). Pressing the A/C "snowflake" button and turning off the A/C compressor will drop the idle speed back to the normal steady 1100 rpm "high-idle" for 15 sec and then it will slowly drop back to a normal 600 rpm warm idle. I always wait 20 or 30 seconds to allow full lubrication circulation before putting any load on the engine anyway, so it's not a major concern.

It seems to be a minor anomaly in the cold idle speed regulating software. This is the sort of issue that can sometimes be corrected by an engine management software update if enough people complain, but it really does not affect the car's drivability unless you want to begin driving immediately upon start up.

On the F25 BMW petrol engines, the engine speed is regulated by a very complex throttle system that uses both a conventional throttle “butterfly” valve and the variable timing/variable lift “Double-VAMOS” BMW cam modulation system. It’s a complex electro-hydraulic system and also uses a very high amount of exhaust gas recirculation at idle and under light loads. It’s stable once the engine oil pressure stabilizes and the exhaust O2 sensors warm up, but can oscillate for the few seconds after start up when everything in the engine control feedback system is changing rapidly.

I liken it to waking up after a deep sleep. Don’t know about you, but for a few seconds after waking, I know I’m not functioning at a “100%” level. Maybe the car just needs a shot of cappuccino in its gas tank.

[carlili4190]

Happens to mine all the time. Took it to the dealer and they said it was "normal"

[xDrive35i]

[QUOTE=Lotus7;10086711]Mine will fluctuate idle speed from 1000 to 1400 rpm for about 15 seconds after a cold start up only if the air conditioner is on (presenting an additional load to the engine). Pressing the A/C "snowflake" button and turning off the A/C compressor will drop the idle speed back to the normal steady 1100 rpm "high-idle" for 15 sec and then it will slowly drop back to a normal 600 rpm warm idle. I always wait 20 or 30 seconds to allow full lubrication circulation before putting any load on the engine anyway, so it's not a major concern.

It seems to be a minor anomaly in the cold idle speed regulating software. This is the sort of issue that can sometimes be corrected by an engine management software update if enough people complain, but it really does not affect the car's drivability unless you want to begin driving immediately upon start up.

On the F25 BMW petrol engines, the engine speed is regulated by a very complex throttle system that uses both a conventional throttle

[Nahoa]

I think y'all are jumping to an assumption that there's an anomaly here. Mine does the same thing as have each of my previous BMW's (each with their own sound). Seems to me to be a "warm-up" activity getting the car to a "basic" warm state and ready to roll.

I'm guessing BMW engineers started it once or twice and would have an ear -- not to mention a sensor -- to detect that this was wrong on all our cars.

[Lotus7]

Originally Posted by Nahoa

I think y'all are jumping to an assumption that there's an anomaly here. Mine does the same thing as have each of my previous BMW's (each with their own sound). Seems to me to be a "warm-up" activity getting the car to a "basic" warm state and ready to roll.

I'm guessing BMW engineers started it once or twice and would have an ear -- not to mention a sensor -- to detect that this was wrong on all our cars.

I consider it an anomaly because, first, it's certainly not an expected or "normal" behavior, and secondly, for those impatient drivers who put their auto transmission cars (all US models) in gear 50 ms after the engine starts, the high-speed "racing" could result in some quite unexpected acceleration of the vehicle.

Considering the problems Toyota recently has had and those of Audi (years ago) for bad press from "unintended acceleration" that never really existed (all cases were finally identified as driver error). BMW might want to address this "issue" before some greedy lawyer finds out about it.

It's not something that I find is a problem, since I can wait the 20 seconds it takes to settle down, but there are those who expect their car to be fully functional withing 1 second of start up. Witness the "race" to be first out of most commuter parking lots 15 seconds after the 5:29 arrives.

[Nahoa]

See, for me at this stage it is both expected and normal. I expect the 20 seconds (or less) this takes get the system better ready to do what we need it to next. Could well be wrong, but that's been my assessment. Both my own acceleration and breaking easily overwhelm the influence of this warm-up period. Just seems like a non-issue to me. If it bothers y'all, I empathize.

[fedinand]

This didn't happen in either the 335i or 335xi in 4 years of ownership..so yes it is an anomaly from my experience with BMW inline turbo engines.

[Nahoa]

Hmm, maybe I'm misunderstanding then. If so, apologies for the useless commentary -- thought it was the thing mine's doing which I find completely ordinary for BMW. This is my first turbo BMW, though.

I've owned three 330i's, a 325i, a Mini (dunno if that applies here or not!), drove a friend's 335i, and have driven a host of 7'ers. They all had what I thought y'all were talking about. A higher initial rev, pulsating sometimes a lot and sometimes none at all, settling down in circa 20 seconds with a change in the exhaust note (more distinct with this X3, never really heard it on the friend's 335i only watched the tach).

Anyway, sorry it's bothering you. Hope it either resolves or turns out to be something that's understood and okay.

[Lotus7]

Seems to be one of those "varies from car to car" situations. My X3 35i does it once every (10) starts of so. Only when the car is completely "cold" (or as cold as it can get in a closed garage in July (when it's 95 deg. F. outside. For my car it will only go into this "oscillation mode" if the A/C is on. Additionally, here in the Chicago metro area we are stuck with 10% ethanol fuel blend, which may also affect the start up "balance".

I either ignore it or just turn off the A/C compressor for 15 seconds. I had a 535i loaner for a week and a half and it never showed any sign of the "oscillating idle" (A/C on or off). Also, the 535i seemed to have its cold-start idle set to a slightly lower speed then my X3. On a cold start, I never saw it go higher than 950-1000 rpm, while my X3 goes to 1100-1150 "normally".

As with Nahoa, for me it's a non-issue". It's one of those little "character traits" you find with specific cars (not models, but individual vehicles) that you learn to ignore, and then expect (and possibly even miss).

However, for some people it can be a concern, which is why I commented. The first time it happened to my wife, she immediately turned the car off and came running in screaming "the car's broken".

[Nahoa]

Sorry, wasted y'alls' time. I just listened to the video again and heard the bit in the first ten seconds. The first couple times I was in a louder environment and it I didn't get the degree of pulsing; just sounded a bit raspy and then later quieter.

I do not experience that on my X3. Sometimes the initial rev varies, but much slower and not so consistently up and down. I did have that two or three times on the 325i (relevance may be nil), but it was not at all a daily thing.

Apologies for my misunderstanding.

[Want the thrill]

Mine pretty consistentantly does what yours does in the video but it seems to repeat about 7 times before it is done and mine sounds like it revs even louder. My RPM's bounce from 1,000 to 1,500 when it is doing this. What are yours at when it occurs?

[fedinand]

Originally Posted by Want the thrill

Mine pretty consistentantly does what yours does in the video but it seems to repeat about 7 times before it is done and mine sounds like it revs even louder. My RPM's bounce from 1,000 to 1,500 when it is doing this. What are yours at when it occurs?

Thats exactly what mine does - it stops after about 15 - 20 seconds, and fluctuates between 1000 - 1500 rpms. It would have been louder had I been closer to the X3 - you can hear the engine get progressively louder as I walk up to it, and it ends about when I get right up next to it.

Car has been great otherwise, so I don't know if I even want to bother taking it in. Anyone experiencing any problems they think is related to this. I do wait for the rpms to settle, but I usually do anyway so it really isn't too much of an inconvenience as long as it isn't a sign of anything serious.

[Want the thrill]

Originally Posted by fedinand

Thats exactly what mine does - it stops after about 15 - 20 seconds, and fluctuates between 1000 - 1500 rpms. It would have been louder had I been closer to the X3 - you can hear the engine get progressively louder as I walk up to it, and it ends about when I get right up next to it.

Car has been great otherwise, so I don't know if I even want to bother taking it in. Anyone experiencing any problems they think is related to this. I do wait for the rpms to settle, but I usually do anyway so it really isn't too much of an inconvenience as long as it isn't a sign of anything serious.

Then that is mine to a "T". Mine was reving loud enough the other day that people turned around and looked when I was parked in a lot. I had to let it do "it's thing" but it seemed to go on forever so I threw it in Neutral hoping it would settle down quicker. My loaner 35i that I drove for 2 months didn't do it near as much or as pronounced as this one. I do have to say the loaner acted up when sitting in traffic on the highway. We had been driving 3 hours (all highway) when traffic backed up due to construction. While we were slowly going, stopping, slowly going, the X started to do the RPM jump thing and wanted to go without putting my foot on the gas. It was very strange but only did it for about 2 minutes in slow going traffic. Hope all this turns out to be nothing....

[fedinand]

Originally Posted by Want the thrill

Then that is mine to a "T". Mine was reving loud enough the other day that people turned around and looked when I was parked in a lot. I had to let it do "it's thing" but it seemed to go on forever so I threw it in Neutral hoping it would settle down quicker. My loaner 35i that I drove for 2 months didn't do it near as much or as pronounced as this one. I do have to say the loaner acted up when sitting in traffic on the highway. We had been driving 3 hours (all highway) when traffic backed up due to construction. While we were slowly going, stopping, slowly going, the X started to do the RPM jump thing and wanted to go without putting my foot on the gas. It was very strange but only did it for about 2 minutes in slow going traffic. Hope all this turns out to be nothing....

I haven't had any issues while driving, but you scenario would have probably would have had me going in for service...good thing that was the loaner!

[Want the thrill]

Originally Posted by fedinand

I haven't had any issues while driving, but you scenario would have probably would have had me going in for service...good thing that was the loaner!

Had it been my keeper, I would def. had it checked out, but since it was going back that day after driving it home, didn't worry about it.

[fedinand]

Originally Posted by Want the thrill

Had it been my keeper, I would def. had it checked out, but since it was going back that day after driving it home, didn't worry about it.

I think I would rather have the jumping RPMs than what you describe with the loaner!

[fvfvsix]

Ours did the same thing today. Really humid day, and it had been sitting in the parking lot for six hours. After the fifth or so rev, I tapped the gas pedal. RPMs went to 3k and then settled into a regular idle. It was weird, but didn't seem super abnormal knowing how complex the air and fuel delivery systems on these cars are.

By the way, I have to commend you on your choice of cars. Here's our X3's garage mate:

[fedinand]

[geordie]

My 35i does this on cold start, VERY pronounced, bouncing between 900-1500RPM. Enough that my wife is like "WTF is wrong with this thing?" It does settle down to normal of course, but it really feels wrong to me. I had a 2010 335i before this and it never did this at all.

I'm sure I'll get the "it's normal" or "couldn't replicate fault" when I take it in to the dealer, so why bother.

It makes me feel like a retard though when you're in a parking lot and people are like 'what is going on with your car dude."

[Want the thrill]

Originally Posted by geordie

My 35i does this on cold start, VERY pronounced, bouncing between 900-1500RPM. Enough that my wife is like "WTF is wrong with this thing?" It does settle down to normal of course, but it really feels wrong to me. I had a 2010 335i before this and it never did this at all.

I'm sure I'll get the "it's normal" or "couldn't replicate fault" when I take it in to the dealer, so why bother.

It makes me feel like a retard though when you're in a parking lot and people are like 'what is going on with your car dude."

+1

[fedinand]

Originally Posted by geordie

My 35i does this on cold start, VERY pronounced, bouncing between 900-1500RPM. Enough that my wife is like "WTF is wrong with this thing?" It does settle down to normal of course, but it really feels wrong to me. I had a 2010 335i before this and it never did this at all.

I'm sure I'll get the "it's normal" or "couldn't replicate fault" when I take it in to the dealer, so why bother.

It makes me feel like a retard though when you're in a parking lot and people are like 'what is going on with your car dude."

exactly!