Tiny
POCOLACHRISTIAN
  • MEMBER
  • 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.
Friday, March 8th, 2013 AT 7:31 AM

1 Reply

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,796 POSTS
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
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Friday, March 8th, 2013 AT 10:18 AM

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