Idle Tables \ VSS screw-up

[Carl Summers]

Hi Jason,
       Some engines don't seem to like the 14.7:1 afr bit since it also 
involves the o2 switching....generally the engine will also see higher 
afr's.....If you have larger pipes or bad placement of the o2 sensor it 
will slow the switching rate...partly because the sensor cools down.....If 
you don't already have a heated o2 sensor you might try doing that.....It 
has worked for me in the past when I have run into this...hth's
-Carl Summers

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-----Original Message-----
From:	Jason Weir [SMTP:jweir at worldnet.att.net]
Sent:	Wednesday, August 11, 1999 7:46 PM
To:	GM EFI Discussion List
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