just put a new cam in and now the tach doesn't work, it's not tunned yet if that has anything to do with it, and sometimes it will work at low rpms but once givin alittle gas it quits but most the time it doesn't work period.

 

Wiring is pinched or not connected somewhere. Check it over again to make sure.

 

do you know where the wiring i?

 

to the top

 

If the engine runs smoothly then the PCM is receiving the cam sensor signal.
So therefore I would guess that the output from the PCM in the loom is faulty or disconected.
Find the tach output wire from the pcm and attach a long wire to it and connect it to the signal wire for the tach move it along the wire to find out where the break is and then replace the section. Alternatively, put a new wire in the PCM and run it straight to the tach.
You could also test the wire with a multimeter or similar.
Basically a bit of time and oatience should do it.

 

Can you autotap it? That will connect to the PCM via the OBDII cable and determine whether or not all is OK at least at that point.

 

Hey Bud we just had this EXACT problem during my heads/cam install a week ago.. Only in my case, not only did my tach not work but when we tried to fire her up a second time, the car wouldnt start at ALL. After a solid weekend of wrench time on this car, we were beyond pissed. lol. Started with the basics to see where the problem was, we checked for codes and came up with faulty Cam Position Sensor". Turned out, when we bolted the intake manifold down we had accidently pinched the wiring harness at the back, and had completely cracked it in half.

We took the manifold off, fixed the wires and she fired right up. Tach works like usual now as well, im pretty sure a pinched wire is your problem too.