[Gmecm] TBI Swap - Iron Duke Tech IV

[David Allen]

 For what it's worth all 3 of my junkyard EFI's on boat, Century, and Nova
ran fine with no VSS. Boat still hasn't got one. ;-)
 The Century was originally a 1983 diesel so the speedometer had no VSS. It
had the mounting holes for the optical pickup so adding this in was easy.  I
did add it when I wanted to install factory electronic cruise in place if
the mechanical CruiseMaster (CruiseDisaster). There WAS a difference in idle
after installing the VSS. Without the VSS, the engine would return to base
idle even when the car was moving at road speed. I would take my foot off
the gas at 40 MPH and the engine would fall to 800 RPM. Felt like it was in
neutral. With VSS it will keep up with the transmission. At that time it had
a MAF-based system, not sure what the ECM was.
  With my Nova (and its 1228746 ECM and TBI) the VSS made absolutely no
noticable difference in the way the car ran or idled (other than a warning
code about no VSS signal) This one was harder to rig up than the 83
speedometer.  I was able to mount a factory optical pickup (from a 1986
model speedometer head) in the original 1972 speedometer head, but it took
some drilling and filing.  I had to paint the inside of the speedometer
mechanism black, and leave the rotating arm silver so there was contrast for
it to pick up on. This works perfectly and provides a signal for the ECM and
cruise unit. And it cost less than $10.
  Bottom line - Try it without the VSS and if drivability problems happen,
install one.  I bet on your Jeep it will not matter. You don't have a
canister purge, you're running a manual trans.  As long as the minimum
airflow is set properly there should not be any stalling problems. Just my
opinion!
  Later,
David


> > went...  For VSS, I do not need it do I?... my speedo is
> > mechanical into my Transfer Case so I can just not use the
> > VSS plug and cap it off / pull the wires, right?  VSS
> > shouldn't send any info to the ECM that would deal with
> > anything except shifting the transmission, and your MPH on
> > the Dash Display, correct?
>