Lean Codes P0171 and P0174

EmersonHart13

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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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Also, car runs great. STFTs at idle look fine, but the LTFTs are very high, like pegged at 25%.

I cannot log, just scan... I know lame.
 

Chester Copperpot

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You plan on going to Luke's this week? I can bring my HPTuners if you really wanna log it.

And if you've done all the above and it's still saying lean, it's the MAF. Is it the OEM MAF?
 

EmersonHart13

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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!
 

EmersonHart13

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Is that MAP reading low...?

BARO is 14.5 PSI and car shows 4.5 which is spot on for good vacuum based on what I have read. Also the MAF seems to be reading in the accepted range, albeit the bottom of it.

RE: MAF -Have one I can use? :)
 

bikrboy128

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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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I'll try to look tomorrow at the ltft at 2500.

I feel like I have addressed most of the vac leak locations. I think the next step would be checking tubing....
 

EmersonHart13

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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.
 

bikrboy128

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the o2 voltage should fluctuate from 200-800. sounds like your reading is normal
i think you need a maf
 

EmersonHart13

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A guy on CHC suggested cleaning my rear O2s...

Can you check a maf with a meter?
 

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