Since the most brilliant minds are on this site, hopefully you can explain it to me and a few others having this issues. I put an NB cluster in my 90 for the electric speedometer and when sitting still, it will sometimes randomly bounce or raise and stay at a certain mph. Its all fun and games, but this messes with the ODO also! When you put a turn signal on, it will dance with the turn signal. As soon as you start rolling, it acts like it should.

The speedo is attached from the PCM to the orange wire on the cluster using OEM wire. LS1's put out a 4000PPM wave and I've adjusted the PCM to make the speedo read correct.

Ideas?

 

I'm going to go with you have a small bare spot on one of the wires either to the sensor or to the cluster and its shorting on something intermittently giving putting pulses into the system that dont exist. Does you computer read the same speed variations when you look at the log?

 

Computer reads what it should. Gauge reads what it should at anything over 0mph.