Alright, so i installed my uberdata ecu today with just the stock ls bin, and when ever i run it over 5000 rpms the tach starts going out of control. The car is still running just fine, rpms normal as can be, but the tach drops down to 2k then floats to 4k drops to 3k, it just goes nuts. So i put my stock ecu back in to see what would happen, and it acts completely normal again. What the hell is going on? Any ideas? Anyone seen this before? Thanks

 

Yeah, the same happoens in my LS at about 6000 but I never really got into finding out the cause

 

my car was doing the same thing, but im running TE and i thought it was the ignition module. so i took it out and had it tested, it test ok so i put it back in and then magicly it started to work just fine. i know this doesnt help you out at all...sorry.

 

check your grounds going to the ecu.... specially the one on the thermostat housing. trust me just check them. i