Timing backfiring rough
My 1997 Chevy Silverado 1500 runs rough.
We have replaced the timing chain, spark
plugs, CAM sensor, distributor cap and
rotor...the check engine code still reads
P0301, P0300, and P0146. The Oxygen
sensor is bank1sensor3 (last sensor after
catalytic converter). What could it still be
that is causing rough idle, infrequent
backfire, and low gas mileage?