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Old 07-22-2012, 08:05 PM   #1
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Default Lean Codes P0171 and P0174

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-gt...171-p0174.html
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Old 07-22-2012, 08:55 PM   #2
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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.
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Old 07-22-2012, 08:58 PM   #3
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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?
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Old 07-22-2012, 09:06 PM   #4
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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!
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Old 07-22-2012, 09:16 PM   #5
 
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Change MAF
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Old 07-22-2012, 09:29 PM   #6
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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? :-)
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Old 07-22-2012, 10:53 PM   #7
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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.
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Old 07-22-2012, 11:00 PM   #8
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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....
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Old 07-23-2012, 08:25 AM   #9
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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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Old 07-23-2012, 06:35 PM   #10
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the o2 voltage should fluctuate from 200-800. sounds like your reading is normal
i think you need a maf
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Old 07-23-2012, 07:49 PM   #11
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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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Old 07-24-2012, 11:58 AM   #12
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Apparently you can: Part 1 -The Basics of Testing a MAF Sensor.
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Old 07-24-2012, 09:01 PM   #13
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Time for the lulz...

My car has an LS2 maf... just discovered this adapter:

Home Shop Connectors / Harnesses Delphi / Packard Adapters GM Delphi / Packard - LS2 MAF to LS1, LT1, truck MAF adaptor harness

So that explains a lot!
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