now stumped: MPH bouncing all over on scanmaster in park and driving? anyone,HELP!!

[1985GN]

ok guys here goes round 2 on this problem i have yet to figure out...i am having a problem with the mph bouncing all over on the scanmaster while driving or even while in park while holding rpm's at like 2000. i have not thrown a code 24 for the vss but i decidied to replace it anyway. problem is still ongoing. the cluster is reading hte correct MPH while driving so i dont see it being a problem between the cables or anyhitng. i went to the back of hte connector going to the VSS buffer and tested out the wiring.. with the key on i have a good power on the pink wire, a good ground on the black wire, and i tested the brown wire from the connector to the ECM and it tested good as well. now i also noticed i have a one wire black connector also on the buffer and it is dead when unplugged but has a solid ground when plugged in and the car is running. i have also tried another known good computer and the problem still persists. what am i missing here??? like i said i can rev it up in park and the MPH goes all over the place from 0 to 90 and in between and does the same while driving. is my problem in the back of hte cluster??? this car never had this problme before i just happened to notice it since getting it back on the road with a new motor. i aslo put a new radio in so i checked back there to make sure i did not hit any wires but its good. any one have any ideas on where to go with this one cause im out of options..........thanks to all

 

[mikestertwo]

Check your block grounds. The VSS and the ESC use the same ground on the block.

 

[1985GN]

hmmm do you know exactly were that ground might be?? i had a dolid ground at the vss with the motor running and my tester on it but who knows...should i just try to make my own ground for it to try?

 

[mikestertwo]

It should be on the back of the right head. Follow the BLK/WHT wire from pin "D" on your ESC module. It should go to the back of the head. The ground for the VSS module also goes to that ground terminal.

 

[TurboBob]

scanmaster version

chip vendor and part number

There are some different datastreams available in the chips, but need to be the correct one for the scanmaster version.

Bob

 

[1985GN]

its the newest version of scanmaster..chip is a turbotweak one and a new version....have had these same parts for over 2 years together and never had a problem till i put it all back together this time..i dont know if its a coinsidence or not but never had this happen till now