To troubleshoot a high RPM issue with my Chevy Vortec 4.3L V6 motor has been experiencing, I performed a compression test, leakdown test, and pulled the crank position sensor to inspect it for damage. FWIW, it passed both the compression test and leakdown test.
After I re-installed the spark plugs, wires and crank position sensor, the engine has been running very poorly. There's a tapping/knocking sound and a squeal that seems correlated to crank speed. Additionally, there's a ton of misfires at idle, which seem mostly limited to the #3 cylinder (I got about 1850+ misfires on Cyl #3 in the 2 minutes it took to pull out of my driveway and park on the street). The noises do seem to be coming from the left bank, which has the #3 cylinder.
Again, these symptoms did not exist before I did the compression test, leakdown test and inspected the crank position sensor.
My understanding is that any time the crank position sensor is replaced or even distributed, a crank position sensor relearn procedure (CASE relearn) should be performed. I never had the relearn done. My limited understanding says that the crank relearn is only for misfire detection, and in my area, this procedure is quite expensive, so I don't want to do it if it won't help.
Could these symptoms caused by the crank sensor relearn not being done?
