Codes P0171 and P0174
Bank 1 and Bank 2 too lean
Installed a new AOS during the rebuild as there was oil in the intake tubes Took the oil filler cap off at idle and there was a little vacuum in the crankcase. 2 fingers and little effort maybe three or four ounces of force to get the cap off, as it was definitely getting pulled by a vacuum when it was removed and installed. I searched this forum and believe I am looking for a fairly substantial vacuum leak. Anyone have experience with this? |
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I was hoping there might be a common failure in a component in that area. I'm modifying a web cam to see if I can see where the smoke is originating.
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check the boot that holds the resonance tube in place - it mught be cracked or folded somehow underneath. when you have the resonance tube off check the secondary air injection system - it has a couple of vacuum connections in that area.
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I like the "Jamesp Extreme Super Smoker" that's a great idea.
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Pumped down everything south of the vacuum check valve by connecting a vacuum source (the Extreme Super Smoker in reverse - turning out to be handy) to the check valve itself and pulling a vacuum. pulled the check valve off after about 30 seconds and there was plenty of vacuum. Checked the actuator for the butterfly valve in the resonance tube and it's tight. Can the air injection cut off valve have a constant leak that shows up in a smoke test??? I blew into the tube and that valve is closed at present. Can the butterfly valve stem have a leak?
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Rather than pull a vacuum and then listen to see if any is left, you need to be testing with a unit that allows you to pull a known level of vacuum and watch for any changes: http://static.summitracing.com/globa...-cp7830_xl.jpg Sometimes the vacuum leaks that cause these codes are slow but continuous ones..... |
Thanks for your reply JFP. I used time instead of a gauge. If the system holds a low vacuum for a full 30 seconds my sense is any leak is less than a pinhole. I think I'll go check it for a full minute though. I did listen for a hiss as well and did not hear one. I bought a plastic vacuum pump similar to the one you show to bleed the clutch as it was marketed for use in brake jobs. It would have been a better tool if it was compatible with brake fluid.
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i had the same issue. My AOS was bad, and i also had a kink in one of my boots, which was hidden underneath, and not visible. i also found that there was a hose that came loose below the resonance flap, and a screw had fallen out, which caused it not to work 100%. upon replacing AOS, all 4 boots and clamps, fixing the resonance tube and butterfly valve, and replacing the MAF the codes stayed away. I bought a smoke tester from a local guy who makes them in his garage. here is a link to my thread. i had the exact same codes p0171 & p0174
http://986forum.com/forums/diy-project-guides/43422-replacing-boots-intake-manifold-resonance-tube.html |
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