I purchased a 91 Firebird, that was originally a V6 but now a small block (seller claimed 350, I called BS, he shrugged), Anyways, The ECM is disconnected, the power wire was cut. I'm for the most part fine with that. I would love to rip out all the old harness that is not in use.

However, I have a couple of issues, I want a working speedo, and I don't want a toggle switch and push button starter. I work 12 hour nights, when I get in my car in the morning, I don't want to think, I want to just turn key and tap the gas.

So, what I'm asking, is if anyone can please, kindly help me with this issue.

The speedo doesn't run through the ECM, if your speedo currently works that is, which it sounds like it does, which means it'll be a cable drive.

Also the starting doesn't run through the ECM.

If any of those systems did run through the ECM they wouldn't work with the power disconnected from the ECM.

The ecm for a 91 does run through the ECM and does not run. Hence, the reason for wanting a working one. What I am asking, is if anyone can help guide me with the proper information, and I believe, doesn't VATS go through the ECM?

And none of those systems are getting power.

For the speedometer, can get a 4 out buffer box or the Dakota Digital GI-5 box. The 4 out buffer is a GM piece that was used in some of the MAF TPI Firebirds along with the '90 - '92 TBI Firebirds & Camaro's (also in Caprices).

The SGI-5 box is generally a better solution as it is programmable. If the rear gears or such are changed the SGI-5 box can be adjusted for a correct speedometer reading. The 4-out box can not do this, the pulse stream is set in hardware.

VATs does go to the ECM, but not through it. Since you have a carb the ECM part of VATs has been bypassed.

RBob.

Thank you. All of the pinout diagrams I have found for the ecm are for the V8's. The wires I have do not appear to match what I see in those diagrams for the VSS wires. If I can get any help with what wire and where on the pinouts they are, it would be a big help.

The '90 - '92 TPI and the '90 - '92 MPFI V6 both use the same ECM (1227730). Therefor the VSS input to the ECM (B9 & B10) and pulse stream from it (B11) to the speedometer cluster use the same pins.

The '90 - '92 TBI will show the pin out of the 4-out buffer box.

RBob.