Will a faulty o2 sensor cause my tach to spike?And will it make me eat threw gas?

 

It will give u horrible gas milage yes, but it shouldn't make the tach bounce. That sounds more like your ignitor. What year engine/car u have and when the tach spikes does the car missfire and run bad?

 

90 sc-zc.today it got worse and was going to 0 and spiking all over,and just died on the way home.When i got it restarted it spiked then misfired and stuff.Now it won start,my dash lights dont even come on.But they will if i crank on the engine.The engine will turn but wont stay started.I think its in the dizzy some where.

 

distributor (coil or ignitor), faulty ground wires, bad ignition switch, bad joints in main relay, poor connection on battery connections, bad electrical connection in harness.

 

I feel ya,got a ecu and distributor on the way.Got to pimp the jetta for a minute.With all 306k on it!!!