Fiddling With the Air Flow Sensor
The common tweak of adjusting the idle mixture at the air flow sensor (AFS) to "cream up" throttle response. One tweak which is known to L-Jetronic tuners and that can work on the Digifant cars is to slightly loosen the spring tension on the air flow sensor.
By reducing the spring tension on the AFS you are essentially allowing more air to flow into the intake for a given throttle position. This "tricks" the computer into supplying more fuel at lower RPM, in effect richening the mixture throughout the range up to about 4,000 RPM when the AFS is wide open anyway.
Reducing AFS Spring Tension
To reduce the spring tension, first remove the black plastic cover on the air flow sensor by cutting up through the silicone sealer with a sharp blade. You will see, among other things, a black gear-wheel on top of what looks like a clock spring. A wire clip engages a tooth on the gear-wheel and is held in place by a 7 mm screw.
Scribe a permanent mark on the gear-wheel at the tooth where the wire clip engages (This is so you can go back to the stock setting if need be).
This is the tricky bit: Get a good grip on the gear wheel with your fingers. Loosen the 7 mm screw and wire clip assembly. Don't drop anything, and whatever you do, don't let go of that spring, or you may never get the car to run correctly again!
Now, carefully unwind the gear-wheel 3 teeth counter-clockwise. This is no more than 8 or 9 mm, so be careful. Reset the wire clip three teeth to the loose side of stock. Tighten down the 7 mm screw, replace the black cover with a thin bead of silicone sealer and you're done.
I tried one, three, and five teeth... one didn't seem to do much, five actually reduced power. Three was just right. Stay with three teeth because the down side of too rich a mixture will be increased emissions, and possible damage to the O2 sensor and/or catalytic converter. YMMV.
I can report that this tweak helps solves some perceived Digifant driveability problems (assuming all else is in order). Hesitation is reduced, throttle response is crisper, and there is mildly quicker acceleration in the lower gears due to increased torque. Gas mileage does not appear to suffer much.
Has anyone tried this?
