Afternoon, Folks...

Did a quick search, but didn't come up with anything that directly addressed the problem I discovered this morning.

Fired up the Camaro, after having sat for a week or so (stupid rain...), and headed for town. The first few kilometers, everything was acting as it should. The tach was reading way high, the fuel level increased when I floored the gas peddle, the speedo said I was in excess of the posted speed limit (it's always right, so far as I knew).

Picked up a friend, went to grab a coffee, and en route, met a smokie. Glanced down to see how fast I was going, and my speedo indicated I was moving at roughly no km/h. I noticed later in the afternoon that the odometer and trip meter aren't advancing, either.

This is a near-stock 1991 RS 'vert, with the 4-speed Auto and the 305TBI. Anyone have any suggestions what might be the cause of this problem? I don't want to drive the car too much, not so much because of the unknown speed (I can judge it fairly well without a speedo), but more so, the odometer...It might just be me, but I kinda like to know that every mile is accounted for. And, on an older car like this, I tend to trust the odometer more than the fuel gauge.

Thanks in advance for any assistance!
Cheers,
AR

 

Ba-Bump....anyone...?

 

90 and up Camaros have an electronic VSS that sends a pulsed signal to the ECM. You'll need to crawl under the car on the driver's side and see if the plug to the VSS on the tailshaft of the transmission is still connected and in good shape.

If that is fine, then your other problem will probably require removing the transmission. Its possible the plastic speedo gears the VSS connects to have worn down and are no longer making a good connection to each other. You can remove the VSS from the trans and inspect the gears that way. One will be on the VSS and the other will remain inside the trans, as its on the tailshaft.

 

Did you change rear end gears recently? There are at least two different VSS for the automatic cars depending on the gearing in the rear. Back when I still had an auto, after switching the gear from 2.73 to 3.23, the shaft running from the driven gear to the VSS sheared in half after about 500 mi of driving. I found the correct VSS, installed it, and didn't have any problems after 10k mi.

 

I only bought the car a month ago. It had and still has 4.1's in the rear. Not sure if they were stock, changed when the guy who owned it before me owned it, or what the story was. He put ~30,000km on the car in 9 years of ownership.

I didn't get a chance to check under the car, and since its lowered, I don't know that I _CAN_ check under the car without getting it on jacks or a hoist. Would a faulty/loose/warn plug just fail like that, or would there be warnings...random failure of the speedo, jitteryness in the reading, etc? I _really_ don't want to have to pull the trans....

AR

 

You won't have to pull the trans to check on the VSS. Like Kevin said, make sure the plug is connected to the sensor first. It sticks out of the driver's side of the tailshaft on the transmission. You might have to jack the car up to get under it. I've found curbs I could drive up on to allow me to slide under it when I didn't have access to jack stands, just be careful. If the sensor is plugged in, there's only one bolt that holds it in. Take that bolt out and you should be able to slide it out and check that it's okay. You might lose a little fluid, but I don't remember it being too bad. This will also allow you to look at the plastic gears and make sure they are in good shape.

 

Nope. If your speedo was reading correctly, or near correctly before, a previous owner has messed with the VSS. As other have said, check.

JamesC