Idle Tables \ VSS screw-up

[Jon Fedock]

    In the '165, there is a "Min Pulsewidth" setting. I don't know if there
is such a thing in the '747 though. Whatever you set min to is as low as it
will go (besides off altogether) no matter how bad the block learns are!
Good Luck
Jon

-----Original Message-----
From: Jason Weir <jweir at worldnet.att.net>
To: GM EFI Discussion List <gmecm at efi332.eng.ohio-state.edu>
Date: Wednesday, August 11, 1999 10:43 PM
Subject: Idle Tables \ VSS screw-up


>Quick question, assuming all is mechanically right except for the chip
>tuning, what tables can affect the idle quality?
>
>Basically what I have is a 7747 setup on my Jeep's 258 I have it running
>great except for the poor idle quality, I have what acts like an
>ignition miss but I have replaced all ignition components from the dizzy
>to the coil/pickup/ignition module, wired full battery power through a
>relay to the coil, never mind the plugs/wires/cap and rotor so it
>shouldn't be an ignition problem.
>
>While watching the O2 voltage, when the mixture goes lean the idle gets
>worse.  Making me think its a lean out problem, like how I'd tune a
>Holley carb turn the mixture screw in till it sputters then out, when
>the ECM leans out the mixture it sputters just the same. Without going
>to an open loop idle is there any way to richen the mixture a little at
>idle, when I add fuel to the VE tables then INT and BLM just takes it
>away,
>
>Some readings from the scanner at idle
>
>700 rpm idle - hunts +/- 50 rpm
>130 blm - steady +/- 1
>128 int - steady +/- 1
>10 IAC counts -  +/- 2 up and down with the idle
>35-40 kpa MAP
>0 degrees initial advance
>15 degrees advance in the chip at idle rpm/load
>changing initial timing and chip timing seems to have no affect on idle
>quality.
>
>Anybody have any ideas?
>
>BTW has anyone seen a setting in the 7747 stuff as to VSS pulses per
>mile?  Turbo City sent me the wrong one and it reads half speed. They
>offered what they called a "2-Pulse" and a "4-Pulse" models so I got the
>2 pulse model, I thought that would have satisfied the 7747's 2000 ppm
>requirement or does the 7747 really need a 4000 ppm? I have patched it
>by setting all the VSS stuff to half the chip value but I know thats
>only a temporary Band-Aid.
>
>thanks
>
>Jason