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| 08-01-2014, 05:23 PM | #1 |
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New Member
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N54 Rough starting in varying ambients
Hi,
I’m about to reach my 1 month anniversary with my E89 and overall had a very enjoyable month! I have had a few concerning moments however. One is its rough starting nature at times, the other is the results of its first CA smog test. I have attached some videos capturing what I interpret to be a rough start (for a fairly new and bone stock car that has been dealer serviced anyways…).  Heres an alternating compilation of what i would consider normal starting and rough starting. Some of the rough starts are more towards the end. [u2b]http://youtu.be/EGU4g-XYWsc[/u2b] http://youtu.be/EGU4g-XYWsc Code:
<object width="560" height="315"><param name="movie" value="//www.youtube.com/v/EGU4g-XYWsc?version=3&hl=en_US"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="//www.youtube.com/v/EGU4g-XYWsc?version=3&hl=en_US" type="application/x-shockwave-flash" width="560" height="315" allowscriptaccess="always" allowfullscreen="true"></embed></object> The most striking correlation is that it will almost always start smoothly without any bogging first thing in the morning when I go to work, its typically cool and damp perhaps 65F. When I leave work it’s more like 80F and dry and it with rough start probably >%80 of the time maybe higher. It will crank, then fire a few times, then sound like it’s about to stall before jumping back to life and idling higher than normal with the idle rpm slowly decreasing to a more normal 800rpm or so over a minute or so. I was initially expecting that this may be HPFP failure related, however after some searching it seems like most examples of HPFP failure are vehicles that suddenly stall or won’t start at all and generally are much more dramatic than what I’m experiencing. I’m also getting the impression that this may actually be normal operation and it’s just the ECU reacting to the changes in ambient conditions since previous operation. Although I would expect a fairly advanced vehicle to be able to do this before it ever started to crank… At any rate, my goal here is mainly to make sure that my engine is as healthy as possible and catch any issues before they can propagate to other systems, destroy the cats, etc. Even if the starting behavior is normal, what can explain the high emissions levels? this typically indicates something isn’t running well. I have been reporting an average 24.3mpg, I was also driving in sport mode fairly aggressively for an hour or so before the emissions test to get the cats toasty. Although it then sat around for 15min before going on the test… I see that the BMW maintenance schedule for plugs is 45k mi, given that I’m getting closeish to that number with >32kMi myself, and I have also noticed that ignition coil replacement and plug replacement at a higher frequency is common on tuned N54 I was going to start there. This is again a bone stock car with no tuning what so ever, but this gave me the impressions design margin may be a bit thin here… Any other thoughts or good methods for diagnostics? Cheers, Tyler Last edited by tgrandahl; 08-01-2014 at 05:42 PM.. |
| 08-02-2014, 09:21 AM | #2 |
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Lieutenant Colonel
 
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Don't rule out the HPFP.
Mine was replaced because it started going into limp mode occasionally on startup. But yours might just be on its way out. The longer you leave it the worse it will get. I wouldn't wait for the pump to start failing before taking it in to the dealer. |
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| 08-02-2014, 09:35 AM | #3 |
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Major
 
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I've had the hpfp replaced and mine does this rough start now and then. Fairly rare tho. Rather than the usual high revving start it shudders starting and idles much lower immediately.
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