Mechanics

CHEVROLET SILVERADO PCV VALVE PROBLEM

1999 Chevrolet Silverado

Hi. I keep getting codes P0171 and P0174. I have a 99 chevy silverado 5.3L. I already cleaned MAF sensor and replaced air and fuel filter and put new pcv valve and put new plugs and wires on it. I can't hear any vaccum leaks either so I'm puzzled what could cause this. Any help would be great. Thank you.
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Pocolachristian
March 8, 2013.



Cleaning mass air flow usually does nothing as it cannot be cleaned of all debris.

Most likely causes, vacuum leaks, low fuel pressure, pcv valve, mass air flow failure. The long term trims need to be monitored with a scan tool.

My bet is on a vacuum leak at the intake

Roy