Engine Stuttering, Jerkiness, Stalling with A/C on at low speeds?

[MarkR171]

This has been happening to me awhile now and I just recently found out it only happens when the A/C is on.

At low speeds (1st gear, under 10mph normally,) the car will sometimes dip below the normal idle speed, shake/vibrate then rev itself back up to stay alive. Sometimes, it does not rev and the engine just dies and transmission (DCT) pops into neutral. Sometimes when going slow in parking lots, I'd release the gas and get on the brakes lightly and the RPM's would drop slightly and the car would jerk forward when revving the engine to stay running. Almost hit the curb at a parking lot because of this... car jerked forward as I was braking to a stop in a stall.

Anyone know how I should go about this with the dealer? It's been happening for several months if not a year on and off, and just now linked it to the A/C as the car is flawless with the A/C off.

This is a very dangerous issue and was wondering if anyone else had this problem. I've seen several threads in the past about the engine dying and transmission going into neutral but nothing about it being linked to A/C or my other symptoms. I'm assuming this is simply a software/tuning issue. Car is stock, was flawless when new, I believe the issue started after several software "recalls."

List of incidents:
Stalls / Engine Dying

1. Inching forward in bumper to bumper traffic, A/C on, D mode, sport button off. Car vibrates at lower than normal RPM and dies. (Two times)
2. After coming to a stop at a stop sign, making a right turn at the intersection. Release the brake, apply light gas, car stutters and dies in the middle of the intersection with on coming traffic! (right turn on red)
3. Shopping mall parking lot, slow speeds, over a speed bump, car stutters and dies.
4. Braking for a stop sign at the top of a hill. Car stutters, dies.
5. Numerous (and I mean a LOT of) other occasions where the car felt like it was going to stutter and die but the engine managed to save itself by revving the engine on it's own. All with A/C on.

Jerking forward

1. Coming to a stop in a parking stall, RPMs fall to 400-500 range, car jerks forward while my foot was on the brake
2. Driving in parking lot, slowing down for pedestrian to cross parking lot to stores. Car jerks forward while on the brake because RPMs fell...

Revving to stay alive

1. Often at stop signs/stop lights when coming to a complete stop, the car would rev 1-3 times to keep the engine from dying
2. Inching forward in traffic
3. Reversing, and changing to Drive from Reverse

I'll be giving my SA a call later today. Hopefully I can get him to ride along with me and show him how the car behaves and hopefully find a way to either get reprogrammed or something. I'm really starting to wish I got the 6MT as much as I love the DCT when it works (A/C off)

[BlackJet]

This sounds like a boost / vacuum leak. Something on the intake has popped off letting unmetered MAF air in (N55) or wild MAP readings (N54). The closed loop idle system is trying to regain control over the leak but doesn't have enough control (strangle rev'ing, low RPMs, jerking). Perhaps the leak is small and without the AC the system can cover up the issue, but when the AC is on, the control system is pushed over the edge (no more room to adjust). This is the first thing I would suspect on any turbo car. If thats not the case, then look into (log) the incoming air count and see how that compares to expected values (if you can do this, otherwise BMW can do this). I am shocked you don't have error codes.

Perhaps there is something wrong with the AC, but these system have so many pressure checks (switches) and contol logic that usally if there is an AC problem it just won't turn on.

[MarkR171]

What would be the best way to test that?

[FrankiE90]

Originally Posted by MarkR171

What would be the best way to test that?

Mark you just took ur 1er in for service paid alot of money for it
now ur having more problems -
For u paid out of pocket -
(you still haven't clear'd up things in this thread -
http://www.1addicts.com/forums/showt...=597424&page=3)

do you get a SES light -
what's your dashboard say.

[MarkR171]

This problem is unrelated and has been happening longer. I've seen other threads about it from other n55/DCT owners.

[MarkR171]

Stopped by the dealer today... SA says engine will definitely throw a code if there's a leak, and there is no code. They will come with me for a ride on Friday and will try raising my idle speed with ac on.

[ILoveChess100]

My 135i N55 has turned off at low speeds when using sport + manual mode on the DCT, while also making a right turn and tapping on the breaks and downshifting all the same time (and I always have the AC on). It has happened a total of 3 times now, the last caused me to almost crash into another vehicle because when the engine stalls and tranny pops into neutral the power brakes and steering is lost so you really have to muscle through it to remain in control and thats kinda hard to do mid turn with traffic around you.
Unreproducible at the dealer of course, so now I drive around with a GoPro hooked up to the passenger headrest and a Zoom H1 mic velcroed on the inside of the trunk right above the exhaust, both always recording when I am in the car so as soon as this issue happens again I am going to drive it straight into the dealership and rip them into pieces if they don't get it fixed.

BTW since the last occurence I had gotten the PPK and as part of that they upgrade all modules to the latest software, so who knows - maybe something is fixed, thought it hasn't been long enough to tell for sure.

Good luck with your case!

[MarkR171]

Thanks, the more I know that I'm not the only one, the more relieved I feel that the problem isn't major and related to my car only.

After speaking to my SA, I drove with A/C on the rest of the day and didn't notice any symptoms at all... Very weird, and I'm going to be really irritated if I can't reproduce anything on the day the tech rides with me... only for the problem to come back afterwards.

[SinCalgary]

Also have similar problems though I have not found time to do anything about it yet. Mostly seems to happen on cold start. Backing out of my garage each morning with just my foot off the brake and no throttle the idle jumps up and down with surges up to about 1500rpm, then when shifting to drive it seems to take about 2 full seconds to shift and is sluggish to accelerate. I notice it is better when the car is warmer but still very sluggish to shift from R to D for instance in a three point turn where you are trying to shift fairly quickly it feels very delayed.

Have also had three low speed stalls, generally when the person in front of me stops short while rolling a quick jab of the brake seems to stall it before the clutch disengages.

I drive in Manual with Sport button engaged pretty much at all times the roads are dry/clear. Have noticed numerous other quirks as well like the car jumping forward when stopping with an idle surge and of course loads of throttle delay sometimes bad enough to have to abort a left hand turn with oncoming traffic because it hesitates just long enough to lose confidence.

Still really like the DCT but it is quirky to drive.

[MarkR171]

Sounds like the issue is just the quirks of a DCT?

My car just stalled on a steep downhill speedbump... Rolled over it semi quickly and applied brakes as I came over it and the engine just died. Like you said, before the clutch could engage...

[MarkR171]

Then again, if the issue were just DCT quirks, it would not only be related to ac on...

[SinCalgary]

I will have to turn off my AC and see if it is any different. I always have it on so never considered it could be part of or the cause of the issues.

[ILoveChess100]

I have had major DCT issues. To somewhat summarize

1. On the day I bought the car and drove home from the dealership with about 35 miles on the odometer, put it in reverse and it just surged backwards and stalled. Fixed through a software update after 3 days at dealer.

2. Not long after (around 130 miles or so on the odo) tranny started throwing yellow/red overheating codes while the car was on cruise control on the highway at like 75mph... Again, another software update to fix that. Unrelated to tranny, the battery was also 'near-dead' for some reason, unable to hold more than 20% charge so they replaced it that same service.

3. Around 680 miles on the odo, the DCT started experiencing horrible hesitation when engaging into first, much like the other post describes - to the point where it sometimes becomes unsafe to try and merge or make turns with oncoming traffic. This one I escalated to BMWNA. Again a software update...

4. Between 2k-3k miles on the car now is my current problem with the stalling at slow speeds while making turns and downshifting right before/mid turn. Have yet to prove that one to the dealership.

Overall, I think from a software pov the DCT is complete shit. So far (other than the battery wtf) nothing mechanical has broken, it has all been just software, software, software (btw I myself am a software engineer which ticks me off even more to see such poor software quality in a product costing 40+ grand)

Most of the time I drive city (I am in Orange County) with moderate traffic to/from work on a daily commute of about 13 miles, and occasionally I would take the car out on a weekend run in twisty nearby road, nothing 'strenious'.

Even if all issues get resolved by some miracle and the car runs great for another 40k miles, I am definitely going to get rid of it before the warranty is up.

[MarkR171]

Left my car at the dealer this morning. I went on a quick drive with their "verifier", someone whose only job is to ride along and verify there is an issue, before the tech drives the car. He asked me to drive forward a bit then stop in the dealer parking lot. Twice in the row, my car came to a stop with the revs bouncing wildly.

Will update with what the tech says later.

[MarkR171]

My SA just called me. He says my computer shows I've been running 89 octane fuel for the past 1000kms and intermittently in the past. The past couple times I filled gas was at a Chevron near home with supposedly 92 octane. I wonder if all this time I've been getting problems only when filling at this station.... He told me to take the car back, and start filling at a different station to see if the problem persists.

[ILoveChess100]

Sounds fishy. Knowing how heavily gas stations are regulated, I highly doubt a Chevron is ripping you off with spewing 89 from a 92 octane hose. Also I would think the lower octane would give you problems at wot, not at idle.

[MarkR171]

Actually, since picking up my car and looking at the worksheet, I know it's bs. "Past 5 fill-ups have been with mid-range fuel." I've used 3 different stations in the past 5 fills. There is no way all 3 have 89 in their 92 tanks.

Since I only have a quarter tank of fuel left, I'm going to burn a bit more, fill it up again, and show them the problem is still there in a day or two. They need to stop wasting my time with bs.

[SinCalgary]

Drove around some today with AC off. Much less erratic idling and no near stalls or stalls. Still loads of throttle lag though. Going to keep playing with it, need to book in for an oil change soon and will bring up my issues then and see if I get anywhere.

[Bluesummer]

This happened to me once before, but I think I also had a bad tank of gas, I just throw in some techron fuel injector cleaner and pumped chevron now. Probalem never happened again

[MarkR171]

Originally Posted by SinCalgary

Drove around some today with AC off. Much less erratic idling and no near stalls or stalls. Still loads of throttle lag though. Going to keep playing with it, need to book in for an oil change soon and will bring up my issues then and see if I get anywhere.

Try this for the throttle lag:

- Put the key in the slot
- keep foot off the brake and press start engine
- press gas pedal past the resistance point and hold it down for 30 seconds
- start the car

This resets the throttle sensitivity adaptation. Makes the lag go away until it readapts.

[MarkR171]

For everyone who posted here with issues, please respond to my poll here. Just trying to compile data.

http://www.1addicts.com/forums/showthread.php?t=613703

[Pangloss]

I have not seen any sign of any of this. Not even a hint of a problem anything like these descriptions.