2006 E90 330i Brake pedal causes rpm surge on cold start - Bimmerfest - BMW Forums



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Old 02-22-2018, 08:17 AM
FLFALGUY FLFALGUY is offline
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Mein Auto: 2006 330i
2006 E90 330i Brake pedal causes rpm surge on cold start

Hi All,

I have a 2006 330i with 130k miles and automatic. The valve cover gasket is leaking and I am replacing soon. But I also noticed that on a cold start, the car starts fine but the engine speed picks up when hitting the brake. I am assuming it is a vacuum leak. As soon the engine warms up, there is no longer an issue.

I cant find anything specific after searching for this issue. Is there a cold start system that could have a vacuum leak? I am hoping I can fix while apart for the new gasket.

Thanks!

Dave
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Old 02-22-2018, 10:37 AM
gbalthrop gbalthrop is offline
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Mein Auto: 2007 328xi E91
Quote:
Originally Posted by FLFALGUY View Post
...2006 330i with 130k miles and automatic...on a cold start, the car starts fine but the engine speed picks up when hitting the brake. I am assuming it is a vacuum leak. As soon the engine warms up, there is no longer an issue.
If the car is stationary after cold start, still in Park, does RPM increase when you press the brake pedal, slow when pedal released, and then increase again when brake depressed again?

Is the pedal "hard" more than it used to be when you press it to restart after engine has been off at least 10 minutes?

Does brake Boost or assist seem less than previously (MORE pedal effort)?

On my model, there is NO connection (direct or indirect) between the brake booster and either the engine or the DME, EXCEPT the vacuum line between the booster and the vacuum pump on the left-front of the engine, mechanically-driven off the timing chain.

I would suggest going to RealOEM.com, entering your VIN and looking at the diagram of parts related to Brakes | Power Brake Unit Depression to make sure YOUR model is the same.

If it is, the ONLY thing I can think of is that the booster diaphragm is beginning to leak, requiring the pump to work harder than usual to try to maintain vacuum in the booster unit, putting more load on the engine, and the DME increasing throttle to try to maintain proper idle speed. That sounds a bit questionable, but it's ALL I can think of.

George
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Old 02-22-2018, 03:52 PM
FLFALGUY FLFALGUY is offline
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Thanks,

I will check it out. The rpm climbs a few hundred when I hit the brake in park. The pedal is reasonably firm but I have not had the car long, its been apart for a few weeks. When I release the brake, the rpms drop to normal idle. After a couple minutes when warm, it no longer happens.
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Old 08-15-2019, 01:53 PM
abm1130 abm1130 is offline
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Quote:
Originally Posted by FLFALGUY View Post
Thanks,

I will check it out. The rpm climbs a few hundred when I hit the brake in park. The pedal is reasonably firm but I have not had the car long, its been apart for a few weeks. When I release the brake, the rpms drop to normal idle. After a couple minutes when warm, it no longer happens.
Hey man, did you fix the problem? I have the same issue on my 06 bmw 130i.
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