[Gmecm] TBI Swap - Iron Duke Tech IV

[Jay Vessels]

Hi there!

 > I am currently missing two sensors, the Knock Sensor, and the Crankshaft
 > Position Sensor.  From what I can tell on the wiring diagrams any other
 > sensors I either am not using, or already have!

The knock sensor is a good thing, but you can get your engine started 
and running without it.

The Crankshaft position sensor is more important.  You won't get it 
started or running without that.  I assume that crank position sensor is 
mounted in the block?  Does your block have provisions for that sensor? 
  Does your crank have the trigger wheel?

Or is this a crank position sensor driven from the timing cover (i.e. 
the late model 4.3V6 CSFI)?  Or something else?

I'd say older versions of the Tech4 with TBI (look in S-10 trucks) will 
have a distributor instead of DIS, if that turns out to be a show-stopper.

> mechanical dizzy went...  For VSS, I do not need it do I?... my speedo 

Technically, no you don't need it to get the engine to start and run. 
To get it to run *right* you'll want VSS.  If your MEMCAL is for an 
automatic, and you wire the ECM to think it's in Neutral, then it will 
at least have a stable idle.  For a MEMCAL calibrated for a manual 
transmission, no wiring changes are needed.

Sounds good, eh?

The problem is that in every older cal I've seen the ECM resets the IAC 
position once the VSS says the vehicle is in motion above a certain 
speed.  Without this reset, the ECM can lose track of IAC position and 
your idle won't be right.  I proved just that a few years ago with my 
2.8V6 TBI (1227429 ECM) and it didn't take a lot of work to get the ECM 
confused.  It's in the archives somewhere.

You also lose EGR control, stall saver, and more.  Even if you don't 
care about EGR, the stall saver code is pretty nice -- come to a hard 
stop, or push in the clutch, and hit the brakes at speed (throttle slams 
closed, engine vacuum demand spikes) and you can kill the engine unless 
the stall saver code catches it.  Those are so intermittant that they 
can drive you nuts chasing them.

You'll find that many on this list see a big difference between 
"running" and "right".  It's a testament to the flexibility and 
tolerance of the GMECM systems that they can run as good as they do with 
little code change in a foreign application and without all of the 
sensor information.

It's also amazing how good that old carb'd engine will run with *good* 
engine management.

Jay Vessels
1982 Chevrolet S-10 Sport, 2.8V6 TBI
1984 Chevrolet S-10 Blazer Sport, 2.8V6 (TBI pending)