Hi, I am attempting an LT1 swap from a 93 TA into my 87 Iroc, but at the same time I'm upgrading my dash and wiring to that from a 91. My question is that while matching wires for the ecm to pcm swap, I found that the Vehicle Speed Sensor on the LT1 goes directly into the PCM rather than the VSS Buffer on the 91 dash harness. Is there a way to splice these together so everything works right without bypassing anything that could cause potential problems? Thanks for your input!

 

Cut the wire that goes from your buffer to the I/P and connect it to the wire which is 4000 P/MI output from the LT1 computer.

 

The wire will be the green/black striped wire coming from the buffer box. I just did this, and splice it into the green/white wire on the white plug on the LT1 harness.

 

Might be green and white on your 86, but im going to have to bet his is one of two brown wires.

 

It will be green/black, I'm using a dash harness out of a 91 model car The green/white comes off of the LT1 harness.

 

Im talking about the wire that goes between the buffer box and the speedometer. Where it plugs into the buffer box itself, I doubt gm changed wiring colors between the firebird and camaro for this.

 

All of the wiring diagrams are showing a tan wire except the 89 model which is showing a green/black output but I know that the dash came out of a 91 model car, so it's very strange on what it is, so hook it to either a green/black, or a tan wire where the buffer box would plug into.

Best way to find out is pull the cluster and measure continuity on pin A14 which is the bottom connector on the dash harness and where the buffer box is at to find the right wire.

They didn't change the colors, just the pinouts on the dash connectors.

 

Thanks for the info, should be able to make everything work.