[bmw] re: Sputtering 535i

[jkerouac <jkerouac@xxxxxxxxxxxxx>]

re: Sputtering 535i

    Have you checked if you are losing either spark or injector spray 
at the point werhe you get stutter?  If you have an ohm meter already, 
look for loss of ground to the injectors as a sign that the ECU is not 
triggering them.  For loss of spark, you will see the tach needle drop 
to zero if the ECU isn't firing the plugs.
    The TPS is likely not a problem.
    If you are getting both spark and fuel, then a probable cause, and 
likely to need replacement over time, is the coolant temperature 
sensor.  That will throw the ECU way off.  Also, have you changed the 
fuel filter?
If the sputter still occurs after doing that, the cause might be the Air 
Flow Meter.  The carbon band wears internally, 150-200k miles is about 
their limit.  I wouldn't buy one just to test.  If you can find or 
borrow a used one, try that first.  Any 4 wire BMW AFM from a big 6 will 
be fine.  Or remove the plastic cover of your AFM and watch the movement 
of the copper pointer as you hit the throttle.  You might see places on 
the carbon band where the tip isn't making contact.  So the ECU thinks 
there's no air getting into the engine and stops delivering fuel.  To 
verify, feather the throttle to get the engine at the stuttering point.  
Apply fingertip pressure to the tip at the point over the band where the 
stutter seems to occur.  You can reposition the pointer and tension it 
more by _gently but firmly bending the pointer arms downward using a 
small hook tip needle nose plier.  The first time you do this may be 
frustrating until you get it right, but sure beats spending $300. for a 
new AFM.

'jk
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