1996 Cavalier 2.2L Tach Problems

I just bought a brand new tach for my 1996 Cavalier 2.2L.  I've tried three tachs now and they all read low RPM's...like it will idle at only 500 RPM's at max and i can't even hit 3,000 RPM's with it, i'm pretty sure i got the right wire, it's the white wire from the coil pack, if i'm wrong someone please straighten me out because i can't for te life of me figure this out, thanks.

The correct tach wire is the white wire. It is easily accessed in the wire loom passing over the transmission on the driver's side of the engine under the air intake. It is the only white wire in the loom and heads towards the ignition module at the bottom of the motor close to the firewall. Test your other connections for the tach such as the ignition source (pink 12 gauge wire off the ignition switch) and ground. Use a clean, paint free section of the vehicle's chassis for ground. sparky

Also... might wanna check out the tach your using... i know all of mine had switches on them to switch from 4cyl 6cyl 8cyl ... if your running a 4cyl and tach is set to 6cyl, your R's will be really low.