Hi all, I'm trying to get an 87 TPI ECU to play nicely with a 91 700R4 VSS and speedo. I've tried all combinations and no matter what, the ECU always reports the same speed in TunerPro. I can get the speedo to change, but all of the outputs give me the same speed from the ECU, which is 2x too fast. I'm completely lost.

SOLUTION: Turns out the previous owner tried to wire the VSS into the ECU, but left the buffer box and it's wires. I cut the brown VSS wire (A10) on the ECU and put it on OUT4 , and the speedo wire on OUT1. All switches were off. This got the speedo and ECU to match, finally some soft calibration to fix the 3.73 rear end. I just wanted to put the solution here in case someone else does this swap and has issues.

 

HI,
The 87 TPI ECU accepts 2000 PPM input. Check the configuration on the SG-5. Connect the 2000 PPM output to the ECM VSS input.

 

Yeah I know, but all of the outputs (8k,4k,2k) give me the same reading, always 2x too fast. I'm beginning to wonder if I have a bad box.

 

Ok so I think I figured it out. I unplugged everything from the SGI box, which should disconnect the VSS from the ECU, but sure enough I got the same speed reading So I think that when the previous owners did the engine swap they left the VSS buffer from the old engine in the car, but disconnected. Tomorrow I will look for the brown VSS wire on the ECU and run that to the SGI. There is only one VSS wire into the computer right?

 

Correct

It looks like this, but it sometimes white


The circuit
http://www.austinthirdgen.org/mkport...SS_V8_vinE.jpg

Connect pin F to pin C

 

Yeah I found the yellow VSS buffer for the 1991 305 that was in the car originally, but the pin that should go to the ECU isn't connect to the '87 ECU because I can unplug it and still get a speed reading on the ALDL (2x as much to be exact). Which leads me to believe that they just ran the sensor directly to the computer (note I get no reading until about 20-25 MPH). So I will have to find the ECU VSS input wire in the harness, cut it and run it to the SGI 2K out. Keep your fingers crossed, I'm so close to having my new baby running perfect!