I have a 03 silverado with a v6 and when i accelerate to around 2500 rpm, the tach starts going crazy and i hear a clicking noise coming from underneath the vehicle. The thing only acts up after the engine warms up, it has no problems when its cold. I have replaced the cam sensor, the plugs and wires, the distributor, dist. cap, dist. rotor. What else could be causing this?
Have you checked for any codes? Even if there is no CEL, there may be a code stored.
The tach going crazy indicates that the coil primary is showing multiple excess firing spikes. The noise might be the result of the erroneous mistimed sparks. The first culprit would be the igniter; followed by the coil; and finally the ECM. If you get to suspecting the ECM and the problem has not been cured, try disconnecting the SPOUT connector and see how the engine runs when the tach is acting up.
Some ideas that I hope help.
“While you’re there”, check the resistance on each injector. It doesn’t take much more time and might show that you have more than one malfunction.