re: Subject: Wife wants fixed-'87 ic

[JKEROUAC@xxxxxxxxxxxxx]

re: Subject: Wife wants fixed-'87 ic:

     Symptoms described are typical of a wearing out 
Air Flow Meter.  This assumes the fuel filter is not 
old and clogging (replace it anyway if >10k miles on 
it regardless of what factory recommended service 
intervals are), and the coolant temperature sensor is 
operating correctly.
     Best way to test an AFM is to use a known good 
AFM from another E30, exact model and year not 
important for testing purposes, just testing if the 
erratic engine behavior goes away.
     Inside the AFM what wears is the carbon band. 
This is where the copper tip of the sensor arm slides 
over.  The band can be found underneath the plastic 
cover.  The pointer arm is rotates on the same shaft 
as the flapper arm in the air passage.  The carbon 
band acts as a potentiometer, giving varying 
resistance depending on where the pointer is 
positioned.
     You can either replace the AFM, or try to bend 
the copper arm downward tighter to make up for the 
fraction of a millimeter wear that is all it takes for 
the AFM to act as if it has a mind of its own.
Good Luck,

'jk
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