5.3l Mystery vacuum leak! - The 1947 - Present Chevrolet & GMC Truck Message Board Network

chevyman70 · 02-14-2015, 11:30 PM

So, I've had a problem with my 5.3l swap. It now reads it has a vacuum leak and codes p0171 and p0174 appear. I replaced MAF, intake manifold gasket, fuel pump, new filter, valve cover gasket, pcv, pcv grommet, and replaced vacuum hoses. Ltft reads 10-18% during iddle on both banks, 25% during acceleration and part throttle. When I plug the PCV, the fuel trims drop to 0% during idle, part throttle, 10% during acceleration. So my question is, what would cause the pcv to act as a vacuum leak?

02-14-2015, 11:30 PM	#1
chevyman70 Registered User Join Date: May 2002 Location: Lakewood, CA Posts: 194	5.3l Mystery vacuum leak! So, I've had a problem with my 5.3l swap. It now reads it has a vacuum leak and codes p0171 and p0174 appear. I replaced MAF, intake manifold gasket, fuel pump, new filter, valve cover gasket, pcv, pcv grommet, and replaced vacuum hoses. Ltft reads 10-18% during iddle on both banks, 25% during acceleration and part throttle. When I plug the PCV, the fuel trims drop to 0% during idle, part throttle, 10% during acceleration. So my question is, what would cause the pcv to act as a vacuum leak?



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