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Lean Codes P0171 and P0174

EmersonHart13

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Jul 18, 2007
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I keep getting these on and off on the GTO.... Sometimes they go away before I can even reset it (a few starts). I have been trying to figure out why and I am starting to get VERY frustrated. Between each step I would clear the code and wait for it to come back, and every time the amount of time varies.

First I cleaned the MAF (paper filter) and checked that the intake pipes were sealed.

Next I checked my PCV hoses and put clamps on them because they were not clamped.

Next I pulled the TB and checked the gasket, looked good, reinstalled.

Today I pulled the manifold and changed the gaskets... and it came back.

What's left other than a bad MAF?

Thanks in advance for the help,

John

I also posted this on Tech: http://ls1tech.com/forums/pontiac-gto-2004-2006/1567972-lean-codes-p0171-p0174.html
 

EmersonHart13

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Jul 18, 2007
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Yessir, OEM. MAF reads .8 lbs per minute or just under at idle. MAP is reading about 4.5.

I really feel like it is the MAF, or the MAF wiring... Is there anyway to check a MAF?

I almost replaced the TB gasket today just to do it and check it off the list even though it looks fine!
 

bikrboy128

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Jul 15, 2007
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Wheaton
what's the ltft at 2500 rpm? what about the upstream O2 sensor?
if the ltft is normal at 2500 and lean at idle, i'd check for a vac leak. if the o2 sensor reads lean, check for fuel starvation (low fuel pressure from a clogged filter or bad pump?).
if you can find any vac leaks and the o2 reads normal, i suspect a whacked out maf. i dont have one, but if you're ever up in lisle i could order one from napa through my shop and return it if it doesnt fix it.
 

EmersonHart13

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Jul 18, 2007
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I checked the LTFTs pegged at 2500 rpm and for the most part they were 20% and above. The STFTs were still fairly good, mostly between +5 and -5.

Checking the O2s is difficult with only a scanner. I feel like I saw a lot of 700 and 800 values but mixed in there were several others.
 
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