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Old 10-05-2012, 11:51 PM   #15
Lemonsqr
Registered User
 
Join Date: Sep 2003
Location: Chicago, IL
Posts: 3,133
My Ride: 2001 TiAg 330i
Quote:
Originally Posted by lcoleman View Post
First off, 45 psi is within the Bentley spec. + or - .5 bar is roughly 7psi. Your problem is not likely fuel related imo.

Secondly, does your car have the filter with the fuel pressure regulator built in, or the external one? Edit: Guess the 330i has it built into the filter.

Fuel pressure can only leak via the check valve in the pump itself, the injectors, or the fuel pressure regulator on the return line afaik.
I had a professional smoke test a couple years ago and he couldnt find any vacuum leaks, which lead me to a fuel problem.

UPDATE:
After the fuel pump was replaced, which helped with the fuel pressure, but not the stumble, I replaced the fuel filter. Still has the stumble and gets worse when it gets colder outside. Interesting thing I found though was with the key in the second position (right before you turn to crank), I floor the throttle and let it up. I turn the key to crank (foot off the gas), and the stumble is either gone or a lot less noticable. I wish I had a new throttle body to see if the issue is with the throttle position sensor. Mystery continues........
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