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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > N55 Turbo Engine Tuning and Exhaust Modifications - 335i Tuning > [Solved] Loss of power on acceleration



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      09-13-2019, 06:01 PM   #1
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[Solved] Loss of power on acceleration

I've got an issue that I can't seem to narrow down. i get a loss of power during moderate acceleration only on cold startup. It only occurs if the car has been sitting for hours, and it only occurs within the first 30 seconds of a cold start. After 30 seconds or so the issue stops.

It is most noticeable in 2nd gear. There are no codes. It feels similar to if DSC kicks in, but much less aggressive. Before I begin throwing money at an LPFP, HPFP and 6 injectors, does anyone know what this could be?

Solved: Replaced brake booster vacuum hose and grommet. Problem went away.

Last edited by Welcome to NBA Jam; 11-12-2019 at 11:04 AM..
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      09-13-2019, 06:33 PM   #2
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Quote:
Originally Posted by Welcome to NBA Jam View Post
I've got an issue that I can't seem to narrow down. i get a loss of power during moderate acceleration only on cold startup. It only occurs if the car has been sitting for hours, and it only occurs within the first 30 seconds of a cold start. After 30 seconds or so the issue stops.

It is most noticeable in 2nd gear. There are no codes. It feels similar to if DSC kicks in, but much less aggressive. Before I begin throwing money at an LPFP, HPFP and 6 injectors, does anyone know what this could be?
Just putting this out there, did you get to take a look at the boost numbers when this is occurring?
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      09-13-2019, 07:03 PM   #3
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So going WOT within 30 seconds after a cold start? Who would have thought that would cause an issue...
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      09-13-2019, 08:28 PM   #4
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Quote:
Originally Posted by TheGoodTheBadTheUgly View Post
Just putting this out there, did you get to take a look at the boost numbers when this is occurring?
I have not, but it's a good idea.

Quote:
Originally Posted by weehe126 View Post
So going WOT within 30 seconds after a cold start? Who would have thought that would cause an issue...
Which of these bolded words confused you in the sentence below?

Quote:
Originally Posted by Welcome to NBA Jam View Post
i get a loss of power during moderate acceleration only on cold startup.
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      09-13-2019, 11:16 PM   #5
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Well, enjoy your rod bearing failure.
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      09-13-2019, 11:25 PM   #6
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Is this something that you just started noticing? Because timing is pulled quite a bit when the engine is cold.

Or it could be related to valvetronic motor. But obviously best way to approach this is to log the car
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      09-14-2019, 07:30 AM   #7
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Quote:
Originally Posted by Pladi View Post
Is this something that you just started noticing? Because timing is pulled quite a bit when the engine is cold.

Or it could be related to valvetronic motor. But obviously best way to approach this is to log the car
This has been happening for about 8 months. I initially thought it was the clutch slipping as that was wearing out, but after replacing it and having it mate to the flywheel I have not seen an improvement during this scenario. I'll do some logs on fuel pressure, boost, etc. and see if there's anything weird.
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      11-12-2019, 11:03 AM   #8
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I replaced the brake booster vacuum hose and grommet due to a hard pedal in the morning. After replacing this, the problem went away.
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      11-12-2019, 03:26 PM   #9
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Quote:
Originally Posted by Welcome to NBA Jam View Post
I replaced the brake booster vacuum hose and grommet due to a hard pedal in the morning. After replacing this, the problem went away.
Is this the hose that goes to the solenoid ?
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      11-12-2019, 05:19 PM   #10
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I guess that could make sense as it is a vacuum leak.
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      11-12-2019, 05:23 PM   #11
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Quote:
Originally Posted by Pladi View Post
Is this the hose that goes to the solenoid ?
Goes from the intake manifold to the brake booster. It runs under the DSC module and exits out next to the brake fluid reservoir.
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      11-13-2019, 02:31 PM   #12
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Quote:
Originally Posted by Welcome to NBA Jam View Post
Goes from the intake manifold to the brake booster. It runs under the DSC module and exits out next to the brake fluid reservoir.
I just found my brake pedal to be hard this morning on the first sub 20deg day. Do you have another other info on the replacement of this hose? I have yet to tackle a vacuum line on this vehicle.
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      11-14-2019, 08:28 AM   #13
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Quote:
Originally Posted by PDR View Post
I just found my brake pedal to be hard this morning on the first sub 20deg day. Do you have another other info on the replacement of this hose? I have yet to tackle a vacuum line on this vehicle.
Read through the post below and watch the video as well. They'll help you figure out where the connection is and how to remove it.

One way to do it:
https://www.e90post.com/forums/showthread.php?t=589753

The other way to do it:
http://youtu.be/Lp0a2U0xGBc

Finally, the way I did it:

1. Remove DSC pump
2. Cap off brake lines using ClosetMaid large and small end caps (<$2 at Home Depot)
3. Unclip vacuum hose from intake manifold by pushing down on the white tab and separating the two connections
4. Remove vacuum hose from brake booster by pulling it out of the grommet; you may need to use leverage as it will be under at least some vacuum and is a tight fit
5. Remove grommet
6. Clean area where grommet sits with isopropyl alcohol
7. Press in new grommet
8. Press new vacuum hose into grommet (very tight fit)
9. Connect vacuum hose to intake manifold
10. Reinstall DSC pump
11. Bleed DSC at all four wheels using INPA

You can do this without fully disconnecting the DSC lines, but it is extremely difficult due to space constraints. With how tight my connections were, I couldn't see how it would be possible in my case.
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