high veh. speed reading on computer, earlyy TCC lockup

[nuc]

I replaced the VSS (the optical sensor and blue/green rectagular box) because my speed according to Tlink was jumping all over the place and causing the TCC to lock and unlock. Now the speed according to the computer is high as compared to actual road speed, so now the tcc is locking up early.

What else could be causing the computer to see the wrong road speed?

Thanks

 

[Black Car]

Is the speed stable and not jumping now?

How much faster than you are actually doing?
How do you know it is faster?

What tranny is in the car? May be wrong color gear in tail shaft.
Do you have any kind of device connected on the speedometer cable? Usually near the power master.
What size tires are on the car?

These are a few things that come to mind.
Gary

 

[dpok69]

Where did you get the optical sensor and buffer box from and how much did it cost?

I too have vss sensor problems. SM II shows speeds slower than actual speed. If i am going 90mph it will show 45. But upto 20 mph it seems to be reading correctly. Digital dash reads the same thing. This means that ecm is seeing those speeds.

On my car there is this grey box coupling thats interrupts the speedo cable near the power master. Someone told me thats for the cruise control.

I checked to see if my rear end was correct by marking the driveshaft then taking note how many revs it takes to turn driveshaft once by spinning the rear wheel. It was like 3.21, the stock gearing.

Tranny was rebuilt and i had asked the GN tranny rebuilder to verify i had correct speedo gears. It was good.

Now i have to change either the buffer box or the optical sensor. Any other thoughts?

 

[nuc]

I have the non digital dash, it reads correctly, only the computer is seeing the wrong speed. It only happens after the car is warmed up and been running longer then 10 minutes. When it is cold the VSS is reading the correct speed. The first VSS I put in was from Autozone, but it did this same thing so I returned it and got a new AC Delco unit. Same problem with it reading an elevated speed after being warmed up. It reads from 20 to 40 mph faster then actual.

What else, other then the VSS, tells the computer how fast the car is going, or, what could be causing the VSS to think the car is going faster then it is?[/SIZE

Tranny is ok, TCC is ok.

Thanks

 

[nuc]

Dpok69,

optical sensor and buffer box come as one unit, at least for the non digital dash.

 

[Black Car]

dpok69
That box on the speedometer cable ISN"T for the cruise control.
You should be able to un-screw it and reconnect the cable.

I have the grey box on my car but it is for the GNX type dash.

NUC- what you are describing is exactly what my old VSS Buffer was doing. After 5 to 10 minutes it would start (every .01 to .02 sec) jumping speed all over the scale. Caused me all kind of problems and many grey hairs.
I replaced it and the new one is working like it is suppose to.
You may have a bad new one.

Gary

 

[nuc]

Are they commonly bad even when new? I thought that might be the problem when I installed the one from Autozone, but then I got a new one from AC Delco and it is doing the same thing. What are the chances that I got 2 new VSS's that were bad out of the box?

 

[Black Car]

Do you have another computer? You can swap with a friend to see if that will make a difference but I doubt it.

The 5 to 10 minutes for it to get warmed up is why I think you may have (can be wrong) a bad new one.

Another question-
Does it work correctly the first 5 minutes and then not work correctly after the warm up (10 minute) time?

That is how mine worked before replacing the VSS Buffer.
Plus had a miss at times which was actually the computer seeing the spped exceed the max speed limit set in the chip, which was shutting off the injectors.
Spent 6 months trying to find this miss.

Gary

 

[dpok69]

I took a look at that aluminum box again today.

It looks as if the box can be split in half with the removal of 4 philips head screws. One speedo cable is goes to each to each half and is connected with some type of fitting that looks like it can be unscrewed.

I figure there must be gears or something in the box. I hope i can disconnect the the two cable from that box and directly attach the cables together.

Why would someone put this type of device inline with the speedo cable?

 

[dpok69]

You the man Gary!!!

You did what three GN mechanics could not figure out even after i showed them that box. A problem i had since i had owned the car for about 3 years.

I disconnected the box and reatached the cables together and wala!!!! The speed readings are correct now!!!

Now the car runs smoother and is more fuel efficient. It is smoother cause the torque convertor is working properly now.

My biggest concern is fuel economy. I was getting like 12mpg even though my car was tuned every year. I am still on the same tank of gas after i fixed the proplem and the guage reads full still. I traveld 86 miles, usually the reading would be in the 13-14 gallon range. I would have to fill my tank usually at 140 miles. Hopefully now it will be closer to 300 miles.


Thanx alot again!!!!

 

[nuc]

Well, after puttiing in a new VSS from autozone and it not working I put in a new AC Delco and it didn't work. Went to the junkyard and took out 3 VSS's from 2 '86 GM's and one '85 GM. Put in the first '86 VSS and it didn't work, took it out and put in the second '86 VSS and so far it is working perfectly, with the speed according to T-link not jumping all over the place.

I hope this is the end of this saga.