04-11-2014, 01:27 PM | #1 |
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Upon cold start engine stumbles
I'm not sure just what might be causing this. Before I take it to the dealer to assess I wish I had some idea of the cause.
2014 335i has ~2,400 miles on it. 8SD automatic. PPK and PPE. In the last couple weeks, after it's been sitting overnight -- i.e. it's a cold start @ 40-50F ambient-- when I start the engine the RPMs pop up to ~1,200- 1,500, then within a second it stumbles, with RPMs dropping sharply -- 500 or less RPMs. Sometimes it just stalls completely and needs a restart. After the stumble or after a restart, it runs just fine. I doubt the gas is bad because other than the stumble on cold starting it runs fine. (See unrelated below.) I use only Chevron 91 octane gas. Sometimes Shell gas if I can not find Chevron station. Any ideas of what's going on? Probably unrelated: Likely unrelated or even not real -- I'm still getting to know the car. I frequently switch between Comfort, Sport and Sport+ (maybe once per drive). Rarely, under moderate acceleration, I think I feel a stumble. I think this is in both Sport and Comfort mode. Much milder than the cold start issue. I've wondered if it is "just" the ECU adjusting to my driving or such. Seems odd to me. Unrelated #2: I am not yet used to the immediate high RPMs upon starting -- 1,200-1,500 for 5-10 seconds, but I think that's just the way modern fuel injected, ECU managed cars start. Doesn't seem kind to the unlubricated moving parts. I trust the German engineers on this one. |
04-13-2014, 12:01 PM | #4 |
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The only thing I can think of (I'm no expert here) is a bad fuel pump? Or a fuel pump that is about to go bad? Either way, I would have it checked ASAP. Definitely not even in the realm of being normal.
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04-16-2014, 10:26 AM | #5 |
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11-24-2014, 06:34 PM | #9 |
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I've been having the same problem. Originally started back in June (3,500 miles). Recorded the dash cluster with my phone to show service what was going on (RPM dropping, stalling etc). Every day for 2 weeks the car exhibited the same problems. Service updated the software, and gave it back to me a week later. Few months later, it happened again (every day, videos to prove it). Brought it back in October, another software update was done along with measure the fuel pump for any inconsistencies. Got it back after a week and a half. No dice, did it a few days after I got it back. A few weeks later, I meet with an 'engineer' and he agrees to a "shot in the dark" and has service replace all injectors, coils, pump, and pretty much every other component associated with the fuel system. Got the car back today, started fine this time. Not too happy at this point.
2014 335i xDrive with 4,400 miles on her, NO mods. Bone stock.
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11-24-2014, 07:22 PM | #10 | |
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11-25-2014, 11:53 AM | #11 |
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02-09-2016, 01:34 PM | #12 | |
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02-09-2016, 01:54 PM | #13 |
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Seems like a hit or miss as far as getting the service center to acknowledge this issue. One forum member had a buy back, I was told the behavior is "completely normal".
Haven't had the chance to take it in for a second opinion, but it hasn't occurred recently either.... My thread on the topic: http://f30.bimmerpost.com/forums/sho....php?t=1181727 Buyback Thread on the topic: http://f30.bimmerpost.com/forums/sho...=hiccup&page=2 |
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02-09-2016, 08:48 PM | #14 |
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This sounds like Carbon build up, but your car is too new for that.
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02-10-2016, 12:24 PM | #15 | |
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I know some people who had issues with the BMS intake, replaced it with stock and issue did not go away . They still blame the BMS intake OP, Take it to the dealership, my guess would be a bad fuel pump or faulty injector
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02-10-2016, 02:04 PM | #16 |
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Not sure why the OP is concerned about knowing what the cause of the problem is before taking it to the dealership. Unless we have some experienced BMW techs on here, I doubt any of us is smarter than the BMW service guys when it comes to diagnosing an issue.
If you absolutely have to know, and you have a smartphone or tablet (IOS or Android), get Carly for BMW and their bluetooth OBDII adapter and read the codes. I've done this myself and when the dealer checks the car, they find the exact same codes. Nevertheless, if your car is under warranty, it's going to get fixed - unless you are unfortunate enough to have a completely inept service dept. at your dealership, which isn't very likely.
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08-13-2019, 10:18 AM | #17 |
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Hey I was wondering if you ended up finding out what the issue was? I've been chasing down a similar issue and found that it goes away if i reset the "Learned Parameters" but then comes back 2-3 weeks later.
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06-05-2020, 10:07 AM | #18 |
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Ive been adding to a thread over on 2addicts, I'm having the same issue on a 2016 m235i 23k miles. Starts normally then sudden drop and sputter, then normalizes. Happens every time the car is off for many hours, such as overnight
Did anyone over here find the issue or can share more diag steps that did or didn't work? I fired the parts shotgun once by putting new Delphi coilpacks in, no effect. I've noticed rail pressure comes up to 2500psi on start and is stable, same with low pressure fuel side @200psi from the moment the pump primes. Rail pressure drops to 130psi or so overnight, not sure what normal bleedoff is but that seems reasonable. If an injector was bleeding off pressure into a cylinder I would expect smoke out the exhaust, which there is none. The problem started as a rapid up-down-up-down rpm about 100-200rpm in either direction directly after start. It seems like after charge pipes and intercooler it became worse and does the typical hard stumble after start, but I can't be sure if that was the exact point it changed behavior since the problem wasn't in my mind a few months ago. No stalling however. Spark plugs are OE and new. No other running problems, no codes. I reset engine learned data and adaptations earlier and will try another cold start when I leave work today. Cleaning the MAF also didn't help |
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06-07-2020, 08:12 PM | #19 | |
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It was resolved when I replaced the coils, so I never really drilled down to see what was the root cause. Good luck wrenching! |
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06-08-2020, 10:52 AM | #20 | |
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06-08-2020, 05:00 PM | #21 | |
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The diag might be over, I've had 3 perfect cold starts now. The only things I did were reset engine adaptations, then unplug maf a couple times for startup and clear codes. Since then it's been behaving perfectly. I'm convinced this is not related to the fuel system now after seeing good pressure all the time, as well as flawless initial 1 second of runtime before the crash and bog. Both of those tell me I can rule out lpfp, hpfp and injectors. Since coils and plugs are new those are ruled out. Kinda starting to think it's something learned in over time, or a bug/glitch/conflict because of that, or at least in software not hardware. It was doing it before putting the charge pipes/IC in (or any mods for that matter as others have reported), doing it after coils, yet when I start resetting adaptations and fiddling with the MAF it's now gone. I reset codes after plugging the MAF in so I expect the DME to be using the sensor now vs being in mafless mode, so if it was a bad maf it should be doing it again right now. Very weird problem, hopefully just a glitch, I'll start resetting adaptations a couple times a year if this was indeed the fix. I'll chime back in if I go a few weeks without issue, but I'd recommend anyone else to try resetting adaptations and doing a few cold starts over a few days and see if it helps you |
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07-09-2020, 12:06 AM | #22 |
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I have the exact same issue. It’s been like this for years. Car runs fine, never any other issues. But when I cold start it goes up to 1400-1500 then drops to like 600-700 and kicks off a bunch of lights for a split second and then revs up. Sounds like a race car. 😂 Mine is a ‘14 335i.
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