re: Why Calibrating AFMs? One AFM bump that works.

[alex.fadeev@xxxxxxxxxxx]

JKEROUAC@domain.elided wrote:
> re: Why Calibrating AFM's works.

Before anyone de-calibrates their AFM, looses power, fails emissions and 
crawls to a junk yard to buy a replacement unmolested AFM: 

> Just like with OEM carburetor jettings of the past, the 
> factory calibration of AFMs and other emissions related 
> components is set so that no car will run bad, 

Let's put the horse back in front of the cart.
AFM, and all other engine components, are NOT set to run good, bad or 
ugly. 
AFM is set to provide consistent input to the DME, which is programmed to 
adjust the air:fuel ratio to optimize engine performance/emissions/fuel 
consumption. 

> as an engine ages, it tends to lean out. 

B.S.
There is no linear correlation between engine wear & tear and air:fuel 
mixture deviation. To many aging components result in too many possible 
outcomes.

> Also timing chains stretch.  That causes a retarded cam 
> timing that allows greater spark timing 

B.S.
Chain do not stretch by inches. Minimal slack from stretching is taken up 
by the chain tensioners. 
Same for the belts. Until both get replaced at prescribed intervals.

> When the AFM is out of calibration, then the ECU 
> has to take steps to try to correct the mixture.

AFM very rarely goes out of calibration. 
A friendly tech advisor for our chapter recently had added up all bad AFMs 
he ever encountered in his years of wrenching. He came up with the total 
of 6 AFMs that required replacement. 5 out of them were out of calibration 
due to owner 'modification'. The other one failed on it's own. 

Draw your own conclusions.

alex f

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