My 1992 firebird 305 Tbi the speedometer does not read right it stays at 140 mph as soon as you start rolling. It does it in frwd & rev . speeddo & speed sensor replaced no luck yet. Is the computer toast or is there another problem ? Has anybody had this problem? looking for answers to this problem.

 

Welcome Aboard!

You may need to look into the VSS buffer circuit.

 

Thanks I will check into that as I don't see much else to check on. Does anyboby know were the buffer curicut is for the VSS on a 1992 firebird 305 TBI

 

Are any of the other guages acting funny? I had a bad ground circuit in mine that made it do the same thing. Also do a voltage drop test on the ground between the firewall and the batt. You won't know if the firewall to guage ground is good but you will know if the rest of em are. Voltage shouldn't drop more than .5 volts.

 

welcome back!! havent seen you post in awhile!



robtmyer: if the needle gets stuck, try turning the car upside down and shaking it... lol, just kidding.


theres a VSS buffer box under the dash.. it takes the signal and splits it to 4000 pulses per mile for the speedo and makes a 2000 pulse per mile signal for the cruise control.

most likely, this is the box going bad, and making your speedo go wacko.. id get one used from another car, as they're usually not stripped from salvage yards, and they generally dont go bad unless they get wet..

 

I got a new one from GM but they can't even tell me where it goes at. If I only knew were it goes I could replace it. Has anybody replaced theres on a 1992 Firebird with a 305 TBI ?

 

If it was the VSS buffer box that you got, it is located under the dash next to the ECM. If it was the VSS sensor that you got, it is located in the side of the transmission case.

 

Its the Buffer I got from GM. Because I asked for a D.R.A.C. Buffer with is a Digital Ration Adapter Controler the guy at GM said he would check into it and he called back and said this is the one for my car. The box says buffer asselmby. Its a little white box. I will look by the ECM agian to check if I can find its location.

 

Yeah - I have the same problem. Helps if I take my foot off the gas though...



(Sorry man - I just couldn't resist!)

Hope you find the problem - keep us posted!

Jonathan

 

Found out what was wrong the person that owned it before me got a 700r4 out of a truck and they have magnetic pickup and a reluctor gear as mine does. So this setup has a higher pulse rate that makes it not compatable with the ECM in my firebird. So I have to go take off the tail shaft housing and put the drive gear on the shaft. Then put correct speed sensor in and its driven gear. That will make it good to go.