I just got me a 98 Blazer 4x4 4.3 engine. It has about 189k on it. The tach doesn't seem to be accurate with the revs of the engine. Is there a known issue with this ?

 

No, it is not a known issue. How exactly is it not being accurate?

 

it just seems kinda lazy when revving the engine, kinda hard to explain, it almost bounces around..

 

Perhaps the distributor gear is worn.

 

Possibly the stepper motor that operates the tach needle is binding, or has a poor connection somewhere. The signal originates at the CPS, (Crankshaft Position Sensor) and is sent directly to the PCM. Serial data is sent to the BCM, and the BCM sends the data to the logic module in the instrument cluster. A bi-directional scan tool capable of accessing the BCM can force a needle sweep to see if the BCM can command the tach, and see if it responds correctly. Without the scan tool, diagnosis is difficult.

EDIT: correction

 

thanks for the info captain hook !