Inaccurate tach and stumble at Idle

[cjbennett01]

Hello everyone, can crankshaft position sensors cause the car to momentarily cut out at idle, and could that also be linked to my tachometer reading lower than actual engine rpm's?

[nos4blood70]

The GXP clusters can commonly have the little needle motors go wrong in the gauge.

As for the CPS, on the 3800s it can cause symptoms like that. Not sure on the N*.

[CMNTMXR57]

CKP's are CKP's. The symptoms are/can be the same.

AS mentioned, stepper motors can be bad in any GM cluster. However, what is your degree of inaccuracy? Are we talking ~100 or less RPM? OR are you talking your at WOT and the tach is showing you at idle, sort of thing?

Reason I ask, is that our gauges, be it tach, speedo, fuel level, etc, aren't precision tuned instruments. They're more or less "dummy gauges" and they operate with in certain windows of tolerance. Now granted a tach or speedo isn't going to be as subject to this as say a temp gauge, but still. These aren ISO certified gauges.