[Gmecm] tuning help

[David Allen]

  When starting out tuning my Buick Century I had a similar problem to
yours.  The engine ran rich with a fast idle.  No Check Engine light.  But
nothing I did in Cats RT Tuner would make any changes. I hooked up the ALDL
and couldn't get any data.  Finally figured out there was a bad connection
on the ROMulator socket. The Check Engine light was not working properly due
to a problem in the cluster connector where the cluster plugs into the
carrier.  This sounds stupid but I wasted a lot of time before figuring it
out... :-(  Finally I leaned on the dash a little and the Check Engine light
started working. But only when pressing on the dash... This light had been
working fine previously.
  When it comes to O2 sensors, the more wires the better!  This is apparent
with an AFR meter tied into the O2 signal and O2 ground at the ECM.  With a
1 wire O2 sensor on the left-hand manifold collector (305 TBI in Nova), the
AFR meter always fluctuated. It jumped around as if the signal was "staticy"
and fluttered so it looked like more than one LED illuminated at a time.
  When you think about it, the exhaust system is really a crappy way to
ground anything, especially a sensor with a millivolt signal.  I installed a
4-wire unit which has a separate ground wire for the sensor signal, plus the
heater.  The warm-up time is now faster; plus the signal is way, WAY
cleaner.  It is amazing the ECM could do anything with the previous signal.
Now, the AFR meter shows only one LED at a time, crosscounting happens more
consistently, and the "slightly oscillatory idle" problem is now gone.
  Later,
David



>
>Hey everyone... I just started up my car for the first time since I rebuilt
it... I'm a newby at tuning, and for some reason I can't get the car to go
into closed >loop.. It definately seems rich at idle, and I'm running single
wire O2's... any suggestions on what to try? I've got a 93 Trans Am, using
TunerCat... Thanks
>
>Mike