Tunning 164 AFM

["eroe@domain.elided" <eroe@domain.elided>]

Vlad

No one offered any advice, and maybe mine will be a no good, but:

I have found you can set the AFM up much like one can set the fuel mixture
on an Spica system.  By ear!

Anyway, I had a VW Vanagon that was L-jet injected.  I wanted to make sure
it did not run lean and I was trying to get a bit more power.  I used the
following procedure on it with great success.  My goal was to set it up just
"slightly" rich.  It was an open loop FI system (no O2 sensor).  The same
procedure should work to get the system back to optimal.

Clearly mark where the spring detent is now.  At least you can go back to
this point, if the following procedure fails you.

Get the car up to operating temperature.
While the car is idling, disconnect the O2 sensor and remove the AFM
"cover".
Place a spacer (bit of cardboard, two pennies, etc) under the throttle stop
(at throttle body.  DO NOT TURN THE SCREW) to keep the engine running at
about 2500 RPM
Gently turn the ARM arm and note the change in engine speed.  You are
changing the mixture by doing this and as it becomes lean, it will run
faster and than slower.  As the mixture goes fat, the engine will slow down.
 Likely you have it set way to fat.  Find the point where you get the
maximum speed.  Note where the AFM contact pointer is.  

While the car is still running at 2500, careful readjust the spring tension
until you can get this same maximum RPM.  This should be pretty close to
stochiometric.  If you have a DVM, use it to watch the O2 sensor output.  It
should be at about 0.5 volts +/- 0.5 and steady with the proper mixture.

Remove the spacer, let the car idle down and reconnect the sensor.  You may
also have to adjust the AFM bypass to get through your state's test.  

By the way, I dinked with the AFM on my Milano and only got bad fuel
economy, so I put it back.  Was your result better?

Good luck!

Erik Roe
AROO 
'87 Milano, '66 Spider, '60 Spider Veloce, and a push reel-type lawn mower

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