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help with p0171

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i have a 2012 chevy cruze eco, 70K miles. i have replaced the O2 sensors, the MAP sensor, and now the car is still throwing the p0171 code. It all started with the O2 sensors codes then the map sensor was throwing a code. everything i have read points to the pcv valve in the valve cover and replacement of the valve cover. Im about at wits end here throwing parts at this car, has anyone else had this similar issue here? I can also tell you the diaphragm on the valve cover hisses/sucks air a lot, dunno if that is normal never paid any attention to it?

any help please!!!
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Discussion Starter · #2 ·
so i have replaced the O2 sensors, the MAP sensor, and now the car is still throwing the p0171 code. It all started with the O2 sensors codes then the map sensor was throwing a code. everything i have read points to the pcv valve in the valve cover and replacement of the valve cover. Im about at wits end here throwing parts at this car, has anyone else had this similar issue here? I can also tell you the diaphragm on the valve cover hisses/sucks air a lot, dunno if that is normal never paid any attention to it?

any help please!!!
 

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To the OP:

Kindly create only one thread per issue.
 

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I had the similar code couple weeks ago, thought it was valve cover. I bought a new cover to replace but it turned out to be my boost gauge tubing which came loose causing a vacuum leak. Once I re-attached the tubing the code cleared.
 

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The code is for a vacuum leak....loose/missing dipstick 'O' ring......failed cam cover burst valve or intake manifold check valve...the last two are most likely and generally the manifold check valve causes the burst valve to fail.

All powetrain coverages if you are still within 5 yr 100k miles.

Rob
 

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Have a vacuum gauge with a cone shaped rubber attached to it. Pull the dipstick and idle the engine, should read about 19"/Hg, but am at 1,000 feet above sea level, will be about an inch less for each thousand feet above sea level.

If reading less than this, not sure how much, shop manual keeps this a highly classified secret, but was only reading about 7"/Hg, this set that P0171 code, also a class A code, need a scanner to reset it.

There is a venturi in the inlet to the turbo that create this vacuum, and also a pressure sensor in the crankcase system that also covers all that air space clear up to the camshaft cover and also includes the PCV system. Shop manual does not say when that pressure sensor clicks.

Like Robby said, he also has been around the block once or twice, that vacuum leak can be anywhere. PVC is nothing more than a check valve, only lets air flow toward the turbo inlet, if you kick in the turbo, positive pressure, if that check valve leaks, will kick up that code. Can be as simple as that oil filler cap is loose, question is were to find it. Mine had a minor crack in the left back corner of that disk in the camshaft cover, that was easy to find. Could have epoxied that, but what the heck, PT warranty was still good, let them put on a new camshaft cover.
 

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so i have replaced the O2 sensors, the MAP sensor, and now the car is still throwing the p0171 code. It all started with the O2 sensors codes then the map sensor was throwing a code. everything i have read points to the pcv valve in the valve cover and replacement of the valve cover. Im about at wits end here throwing parts at this car, has anyone else had this similar issue here? I can also tell you the diaphragm on the valve cover hisses/sucks air a lot, dunno if that is normal never paid any attention to it?

any help please!!!
Easy test - see if it's doing that:


Now that you know about us, don't throw parts at it next time :D
 

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Discussion Starter · #12 ·

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Powertrain warranty is 5 years/100k from original date of purchase and doesn't matter where YOU bought the car from. Check my.chevrolet.com if you suspect it's still active.

Yep, don't see the check valve there.
 

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Discussion Starter · #17 ·
Powertrain warranty is 5 years/100k from original date of purchase and doesn't matter where YOU bought the car from. Check my.chevrolet.com if you suspect it's still active.

Yep, don't see the check valve there.
SOB, powertrain warranty expired 6/26/17, just my darn luck

so what is causing this "Non Return Valve" to go missing? does anyone else think this is a dumb design?
 

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It just gets stuck and then sucked in down one of the runners and melted or something. Doesn't seem to cause damage.

Yes, I saw the installation personally on XR's car and know of several others that have been running it for a while now. It's actually mostly hidden from view from the top - very clean.
 
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