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10 Silverado 4.8 high LTFT both banks

  • Stryped
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7 months 1 week ago #82811 by Stryped
10 Silverado 4.8 high LTFT both banks was created by Stryped
My son has a 2010 Silverado LS with a 4.8 and around 150,000 miles. It is getting a recurring code for 171 and 174 indicating both fuel trims are lean. Truck drives fine but once in a blue moon the service stable track light will come on. It will eventually go back off. No obvious vacuum leaks that I can tell. LTFT at idle with engine warms is in upper 20’s for both banks. MAF sensor fluxuates from  .42 lbs/minute to .81 lbs a minute. While ideling, if I remove the MAF sensor connector, LTFT goes to single digits. I will attack some scanner screen shots . Can anyone please help?
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  • Noah
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7 months 6 days ago #82952 by Noah
Replied by Noah on topic 10 Silverado 4.8 high LTFT both banks
If the fuel trims are positive at idle but improve at higher rpm, then it very well may be a vacuum leak.
If you checked with a smoke machine and brake clean and still can't find a leak, consider the purge valve may be sticking open.
"Ground cannot be checked with a 10mm socket"

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