91 Camaro Rs 305 TBI

While driving the other day my speedometer jumped up then dropped all the way down and stopped working. Every other gauge still worked fine.

I went home got under the car and cleaned the sensor then went for a test drive and it was still not working..

However today while i was driving it just started working again on its own?

What could be causing this? Im really hoping its not the VSS..

 

More than likely it's a intermittent open / short fault in either the yellow or purple wire, common area problem is at the vss and is not visual. The only way you can really be sure is to test the wires via an ohm meter from the vss to the plug at the computer. Un-plug both ends and loop your test set between the two connectors and wiggle the wiring at the vss. Commonly, the wires at the vss break down right at the area where it makes a 90 deg bend. When it goes open your speedo quits. When it finds connectivity, the speed registers again.

If you find a fault in either wire at the vss but are able to reconnect the circuit without cutting (and fixing) the wire is to add a simple tie wrap to the affected area. It's not the best solution but it may work for you. It has for me.

Also, the wiring connection must be good at the trans. The best way to ensure that your connection is good is to connect the vss lead and test with your ohm meter back across the circuit. If the loop is good then your speedo will work. If the connection is poor, it may or may not work. Again, try the zip tie fix around the connection. That's another quick and dirty fix but, it may work if the connection isnt staying put.

Good luck