My tach is jumping all over the place at idle and the engine misses real bad while driving. also, i have t56 so i have the SGI 5 box hook up, well now the speedo is bounsing all over th eplace too just like the tach sometimes the speedo stays at 130 while i am stopped an the odoemeter racks up miles just sitting there. the speedo will stop bouncing if i take the fan fuse out. i cant figure it out. all these problems started at the same time: engine misses and ships, tach and speedo bounce all over the place, engine stalls after 30 seconds of running, and sometimes it wont start at all. what is hapening here. wires, plugs and dist are new as well as all the sensors.

 

that is odd. I had alot of the same symptoms...albeit not all of them..when my 6AL went bad. I'd try bypassing it and going back to the stock ignition to see if anything changes.

 

Doesn't the ECM require input from the VSS? If you are sitting at idle the the speedo and odometer are still rolling it's gotta be messing up the ECM's mind.

 

I bypassed the MSD box already and it does the same thing.I also put my stock coil back in and it didnt help. ALso. i have been running the car without a speedo hooked up for a month now and it never acted up.