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Old 03-23-2013, 12:49 PM   #6
White_Knuckles
Registered User
 
Join Date: May 2009
Location: Washington (the state)
Posts: 1,452
My Ride: 2003 325xi
This is a tough one. There are several variables to what might be the culprit. The fact you can hear the pump spin up is good but you can't tell what the pressure is at the fuel rail. A failing pump or restricted filter will duplicate that symptom as well a sensor, etc. I fought a failing intake cam sensor that had symptoms that were similar with stalling. My car would intermittently die with never a code to be thrown. I got lucky and a new sensor cured the evil. That does not suggest it's your issue just pointing out how mysterious chasing these problems can be.

You need to isolate the problem and solve for what's happening before throwing parts at it. Is the car starved for fuel when this occurs? Is the DME going crazy with inputs like the TPS drifting? The only way to tell is getting a diagnostic monitor on the thing. There is a very reasonable software logger out there that does this well. It costs around $50 and you'll need a $10 USB-OBDII cable. So for $60 you'll have a proper tool. The next trick is reading and interpreting what the data graphs mean. They provide base-line graphs of a healthy engine to compare to. Takes some of the rocket science out of it. You may be able to detect a lean condition from O2 behavior (Lambda) or a twitchy TPS just observing the sensor outputs. The other option is getting a shop to perform a diag. with their spendy equipment to help narrow this down. A shop minimum fee can be less then the hundreds you may spend tossing random parts in.

You're describing your symptoms well but advise from member (guessers) can absolutely send you down the wrong bunny trails. You need to establish more facts before diving in. I had an issue where the car started but any demand (pressing the throttle) lagged terribly. It would magically clear up. Finally, the car would start-die-start-die and then would not start. The fuel pump was the bugger and that day, it would no longer spin up. Again, I was lucky that it croaked before I chased all the wrong things assuming it was okay. Don't wait for replies that tell you what's wrong 'cause we can't possibly nail it from a crystal ball. You have to pin down the issue either guessing with random parts or collecting facts such as fuel pressure readings, diag. monitor/logger results etc. Sorry, but it's really how much you are willing to investigate with the proper tools or reach out to a pro. Below is the logger software link. >>

http://bimmersoftware.com/bmwlogger

Edit: Wow! Don't rev that thing that high (5-6K) without a load (driving). It's NOT good for the engine.
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Last edited by White_Knuckles; 03-23-2013 at 01:04 PM.
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