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Old 03-01-2010, 09:41 PM
bluebee's Avatar
bluebee bluebee is offline
Seek to understand,^Value
Location: San Jose, California
Join Date: Mar 2008
Posts: 25,236
Mein Auto: 02 BMW 525i M54 auto 130K
I'm hoping someone like QSilver will have a PDF of how the fuel injectors actually work that shows the timing between the 7 injectors on the I6.

Meanwhile, I've done nothing (placebo effect) and the problem has "fixed itself" (which is to say it's frustratingly rare and intermittent).

Having read everything I could find (always willing to read more if you have a good reference), I'm beginning to hypothesize the following sequence:

a) Misfire occurs in cylinder #4 for some reason (unknown why as yet but it could be a temperature/humidity/sitting-for-two-days glitch)
b) Misfire continues enough so that DME cuts off fuel for injector #4 (assuming fuel injectors fire directly into the cylinder in an '02 525i)
c) Apparently even if the misfire corrects itself, the fuel is still cut off from cylinder #4 FOREVER and ever (or until the next reset)
d) The ONLY thing that returns fuel to cylinder #4 is for the ignition to be cycled <=== this is my hypothesis based on my observations
e) When the ignition is cycled, fuel returns, and the minor glitch (I'm thinking it's due to software) doesn't occur on restart conditions

Please feel free to pick apart my hypothesis above as that's the only way we'll get to the bottom of this glitch.

Under this hypothesis, the minor problem of a software-confused misfire causes a more major stumbling when the cylinder is PERMANENTLY starved of fuel BECAUSE that fuel cutoff is never reset (so the hypothesis goes) until the ignition is cycled.

Does this hypothesis make sense?
If so, does it afford a test sequence for us to prescribe for when it happens to one of us?
Attached Thumbnails
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Attached Files
File Type: pdf L-Jetronic Fuel Injection.pdf (162.5 KB, 820 views)
File Type: pdf L-Jetronic_Fuel_Injection_For_BMW_E12s.pdf (579.0 KB, 295 views)
File Type: pdf L-jetronic page.pdf (106.4 KB, 249 views)
File Type: pdf 912E_FI_Technica_Manual.pdf (509.4 KB, 206 views)

Last edited by bluebee; 03-07-2010 at 07:31 AM.
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