2001 Blazer. 4.3 Vortec. 2WD. 4 door. Engine replaced with a rebuild at 120,000. Current mileage 168,000. At start. Engine idles smooth. Engine revs up smoothly and without observable issue to 3500 RPM. Drives normally and without observable issue in first gear. *At shift* from 1st gear to 2nd gear, Tach goes erratic. Engine stumbles and struggles to stay running until you stop and put car in park or engine dies. Wait 30 seconds. Restart. Engine idles fine. While erratic behavior engine appears unresponsive to accelerator. Does not matter what position you set the accelerator with your foot, the engine appears to be struggling just to stay alive.

CPS Sensor replaced in Oct 2023. This is the car's 3rd sensor. Standard Motor Products. Just 20,000 miles on this sensor. This sensor has an integrated analog to digital convertor in the sensor to encourage a "clean" signal to the PCM. Blazer has been running without issue until first week of December. Only notable change was very damp humid weather. Then car started acting sporadic struggling at light to non-drive able over a course of 3 days. Pulled DTC code P0335 = Crankshaft Position Sensor "A" Circuit Malfunction.

Please see attached images. There are fine cracks in the sensor between where the different metals are encased. Is this acceptable? Normal? Could this be contributing to problem? If I replace again, is it acceptable to add a washer of a few thousands thickness to back sensor away from getting rubbed?



Slight rub mark on one spot on crankshaft.

 

First, I would not "upgrade" the sensor. The engine computer expects a certain waveform type as designed. Second, after a crank sensor replacemnt, you need to do a case relearn. Third, if you have interference as is suggested looking at those teeth, you need to shim the sensor to get the proper clearance.

George

 

Looks to me like it is hitting the reluctor wheel. They make shims for that.