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Discussion Starter · #1 ·
04 v8, 96k miles on the clock.

PO171 & P0174
System too lean, bank 1 & 2

Vehicle runs completely fine, its smooth, power in all gears throughout rpms, city, highway, rolling. Averaging about 12.8 mpg. (I have had the car for about a month now and those are my personal observations as is)

I'm trying to figure out what's the problem.
First, i looked at all the vacuum lines; some had cracks but went ahead and replaced all of them just as a precaution. Both diaphragms collapse when engine is started. When I turn off the motor, both pop open a few minutes later.

Checked the air bubble reservoirs down under the LH front bumper, both are fine no physical damage, and both push back when blown into (as if there is a balloon inside)

Inspected intake filters, clean.
Inspected the intake pipes and "Y" hose, no cracks.

Then removed the intake manifold, and inspected everything on there, had a few bolts loose, matter of fact on the inside. They were the small zinc plated ones. You guys may want to check yours as well before that gets sucked into your cylinders.

Also found out someone just changed their spark plugs and the codes never came back, so I decided to change mine with NGK BKR6EIX [6418], during the process I noticed all 8 coil packs must have been changed recently since all are clean and shiny still, no corrosion or surface rust. But the codes still came back.

Now my thoughts are starting to think about the maf sensors, oxygen sensors, and/or the fuel system.

Fuel filters are cheap to do so I'll go ahead and get that done next, but my concern is it might be the fuel pump...

But before I go to the fuel pump, I'm trying to see is if anyone has tested their oxygen sensors and/ or maf sensors through an ohm meter and if someone can provide the information on how to test them, I would really appreciate it.
 

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If you have VAG COM you can log/observe the MAF sensors as well as the O2 sensors. If you do not have the software, you really need to invest in it. This isn't the last time you will need it.

This should help...

http://www.ross-tech.com/vag-com/cars/fuel-trim.html

"Here's a good sanity check for the status of your MAF. Do a full-throttle run all the way to redline in a single gear (second works fine). Group 002 usually shows air mass in g/s. Your peak airflow should be roughly 0.80 times your horsepower. So, if you have a stock 150 hp 1.8T, expect around 120 g/s. If you see significantly less than that, you MAF may be on the way out. "
 

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Discussion Starter · #3 ·
thanks A8AWD, im already trying to obtain a vagcom, but would like to do simple things first.

can someone compare their crankcase vent valve with me?

as soon as i start the engine, its sucking in air, as if its fully open, and remains that way through revving, and when hot. my question is, isn't it only supposed to be sucking air say under load or when revving? not at idle.

if someone can confirm this, id highly appreciate it. i have a feeling this is where my issue resides since most of my lean readings are during idle.
 

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rwdanthony, it is HIGHLY LIKELY that is your issue. If it's sucking air, then it's likely in need of replacement. Air going in will cause lean fuel mixtures as oil vapor isn't being sucked out of the crankcase. The internal diagram is probably broken in pieces (rubber I think) and in need of replacement.
 

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I had same code and issue was crank case vent - it should NOT suck any air. Replace it yourself for $55 at eBay.
 

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rwdanthony, So.. what was your issue and how did it get resolved ? I am having the exact same 2 code issues showing up on my 2006 V6 ?
About to do all of the things you talk about here... Thanks for your reply..
 
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