Where are the VSS Signals and do I need them?

[87gtVIC]

Car is a 1987 Crown Victoria.

Undergoing HO conversion. I want to retain cruise functions. New computer (A9P) is calling for VSS+ on pin 3 and VSS- on Pin 6.

Is this necessary for my 1987 vehicle with an entire computer dedicated for the cruise control?

If so, where the hell do I find those two signals?

I provided a diagram where they might be found......



Thanks!

-David

[gadget73]

They come into the cruise control module. You can find them in the harness that comes up from the transmission. The ECM is happier if the VSS wires are there. With no EGR it may not matter quite as much but I had some slight misfire problems when coasting that went away with VSS. It really makes the EGR system run retarded though, and it causes an annoying off-idle hesitation.

[87gtVIC]

So it has nothing to do with retaining cruise in my situation...

I put up a diagram of the cruise control module (speed control amplifier in the EVTM's case). Which ones am I looking for? Nothing appears to be coming from the tranny......

I'll add them if they can be found here and on the car too regardless if I am retaining egr or not...which I am not due to the heads I have. Its nice to have all of the wiring done though if I were to ever go to a different head/intake combo.

[sly]

nope. 88-91 are the bastard years with the cruise integral to the ECM. The ECM will be happier for idling down at stop and off-idle with the VSS connected... or at least it was that way with that Lincoln I had. But I'm sure it's got a funky cam in it because it will NOT idle nice and smooth. (at least not while I had it.)

[87gtVIC]

Doing a bit more digging got me here:



I saw the words "to sensor" on the dark green with white stripe wire as well as the black wire. I then look back to my original post and see the same thing.

Are those the VSS+ and VSS-?

[sly]

It should be.

[gadget73]

yes. Sensor is VSS. You can tap them anywhere it's convenient. The only place it should be going on your car is the speed control amplifier and to the tripminder. VSS- is just ground.

[DerekTheGreat]

Sorry to inject myself in here buut.. My car sometimes has off idle hesitation. Even though the speedo is mechanical the trans has a VSS?? Could this be my problem after all? If you come to a stop real fast you can feel the engine idling funny too, like part of what sly mentioned..

[sly]

If the cruise works... probably not. If you have an HO swap and the VSS line is not sent to the ECM, possibly.

[DerekTheGreat]

Cruise works fine, ends up cruising 1-3 mph slower than where you set it though.

[86VickyLX]

I added the input back when I was having EGR issues and they ended up going way. It's still hooked up. It gives a digital readout as to how fast I'm going with the quarterhorse. Very useful for datalogging. 87 and down and 91(Lincoln) 92-94 have standalone cruise.

[87gtVIC]

Great. Thanks everyone. In the notebook it goes, along with all of the other wiring and vacuum changes I have jotted down.

[87gtVIC]

The VSS harness was really easy to find on my car (1987 Crown Victoria). It was just a two wire harness wrapped in black tape starting from under the ECM connector and heading over the engine to a connector just above the passenger side head and down the passengers side of the transmission then jumped back over to the drivers side and eventually hitting the VSS.