Jumpy Tach on '97 regal 3800 series2

[Joker649]

I have done lots of reading and can't seem to find anything that matchs my problem. Today my tachometer started jumping way up (2000-3000 higher then actual) then back to actual. When this happens the ECM seems to react and causes the car to "Chug" and when at low enough revs can cause the car to stall. All the other gauges look fine, the service engine light is flashing but i don't have a tool to read it. I remember something about shorting to pin and reading the codes from the flashing light but have never done it on this model year.

Does this sound like a crank sensor? Could this be a ground problem? Maybe an ignition switch problem?

Any help or advice on this would be greatly appreciated.

Joker649

[BNaylor]

It sounds like plain misfire. A flashing SES/CEL light indicates a misfire on one or more cylinders.

You cannnot short out pins like on odb-i. Odb-ii requires a scanner to read the codes.

Try new spark plugs and wires first.

Also make sure battery connections are good especially the grounds and charging system is putting out.