91 Camro RS 305 Automatic
Speedometer/Odometer works intermittently. Some days they work and some days not (they both stop working when the fail). The cruise control works whether the speedometer/odometer is working or not so I do not suspect the Speed Sensor (could certianly be wrong). Any ideas certainly appreciated before I pull things apart.

New to rebuilding/restoring a car but trying my best. This site has just been a God send at times. You guys are great!

 

I dont know what is wrong, apparently no one here does either as no one answers these questions. Mine does the same thin and I still haven't figured it out.

 

theres a vss buffer box, either under the dash near the computer, or on the back of the cluster itself. if it fails the speedo doesnt get the vss signal, causing it to not work. the vss sends a signal to the ecm and this buffer box, then the buffer box drives the speedo. cable driven speedos just have a cable that plugs directly into the speedo and are much simpler to diagnose.

 

this is for tbi only, tpi and v-6 cars the ecm controls the speedo.

 

Mine is doing the exact same thing. Has anybody fixed yet?

Thanks
Speedy

 

Pull your cluster out and test the circuit from the ECM to the connector on the dash. See if your getting continuity. If nothing then you know you have a bad connection between the ECM and the dash connector. If your looking at the connectors on the DASH side then your Speedo wire will be on the Driver's Side Plug (C2) top left corner wire (1st one) and the color should be brown. Although you wont see the color from the front of that connector.

And as Travis said the only Camaros with a VSS Buffer box was the 88-92 TBI cars.

 

the speedo circuit is pretty simple. theres the vss in the trans, the wires going from it (to the buffer box if tbi), the ecm, and wires going from the ecm (or buffer box) and the speedo itself. since the odo is tied into the speedo if one stops, both stop. chances are you just have a loose connection somewhere

 

I have the same problem with my 89 RS but my speedometer jumps rapidly from 50 to 90 and back after i hit 60...any thoughts on this??

 

I think the 89 has a cable driven speedo, probably a failing cable. Binding, it grabs and releases in the housing.

For the OP the speedo has an electronic circuit that actually runs the little motor/circuit that actuates the speed and mileage deal. Could be going bad there.

 

I haven't been able to track down my problem, I think I will just parts out this lemon and never buy a camaro again. Drives great, looks sharp, but very unreliable.

 

saying that shows youre not a true fan of these cars. have you even checked to see if its an electric or cable driven speedo?

 

Actually I am a fan of these cars,but, the electronics are crap to say the least. It is a TPI ecm controlled speedometer. I'm sure at the time of the inception of this cars manufacture, it was a "brillient" idea. But, ( from what I have read on this forum), it is an especially prevailient problem. I have owned two other Z-28's inthe past ,(2nd gen.) , and they were reliable to the nth degree even when I beat the crap outta them. This one breaks too easily for me. They look really sharp, handle better than previous models, but are extreamly unreliable inthe electronics. When I have to tear a dash out to track down a loose wire to operate my speedo, or replace a capacitor in the tach, or any other miriad of things that have me ready to shoot his pig, it isn't a car you can enjoy driving. Just my opinion, like I said will parts out his car for some one else to repair their broiken Camaro. I will hunt down an older z if I want to enjoy a hassel free experince in owning a car.

 

where are you located and how much you want for the whole car?

 

Don't tear out the dash. I don't know why you would do that before anything. You have a vehicle speed sensor on the side of your trans, near the rear of the trans (right before the driveshaft.)

This sensor is held by a single (10mm I believe) bolt that holds the sensor in. These sensors are driven by plastic gears that may slip. Check them out to see if they are stripped.

 

like i said earlier, the VSS is a simple circuit. it can only fail in a few places.

 

I've been having the same problem..Intermittent odometer and speed jumping. I've replaced the buffer and put in a new cluster. I've checked power feeding the buffer(pink wire) and I have battery voltage. Then I checked the (green wire)feed off the buffer to cluster it has continuity from the cluster side to the buffer side.. I then checked the same green wire to ground and it not grounded. I am planning on changing out the VSS itself next unless anyone has a better idea??

 

sounds like youve ruled everything out but the vss. or the wires from the vss to the buffer box.

 

ok, here's an update....My speedo is jumping intermittently when the car is in park. This is also showing up in my datalogs. I've replaced the cluster,buffer,and VSS with no change. I've also checked the voltage at the buffer. Pink wire shower battery voltage with key forward and green wire is approx 2 volts less then battery. The green wire goes from the buffer to the cluster. I check it and it isn't showing an open and isn't showing continuity to ground. I'm wondering if it could be possible that my MSD could be effecting the speedo, being the MSD wiring is close to the purple/yellow wires off the VSS??? Any ideas?

 

If it's easy to bypass and test, I'd certainly do it. I've seen all sorts of problems with MSDs in street cars. And most of the time it seems to be intermittent issues.

 

I seem to have a similar problem except my speedo is always right, it is a 1991 z28 with a tpi auto, my odometer works at its own speed when it wants too but i have been a gear head too long to just throw parts at it till i get lucky,, has anyone fixed this problem? what was the problem , how did you diagnose it, and what did you replace to fix it? Timmy

 

I had the same problem untill it stopped working at all. I think is something in the speedometer wiring under the car.

 

Can the Vehicle Speed Sensor be damaged by water contact if the wiring contact wasn't properly sealed?

 

Timmy, I'm with you, man. I've got the same problem. 92 Firebird 5.0TBI. Speedo is always correct. Odometer worked intermittently for for a while, then just stopped working. Anyone know the cause? Where to look first? Rip out the dash or under the car?

 

I think it was the VSS.

 

did a new one make your odometer work again? the whole "think" in your statement makes me apprehensive, $110 for the part is alot to throw at a maybe and in my case the speedometer doesn't jump around and is always right its the odometer that isn't moving except when it wants to so in my mind my VSS is working. Im not trying to be a D*ck but im sure I don't own the only camaro to have this problem just hoping someone else has fixed it and can tell me what to trouble shoot,. Timmy