Found Codes: P0171 & P0174

[04silveradomykk]

Bank 1 & 2 lean condition. Could be any of these causes via www.obd-codes.com (http://www.obd-codes.com)

The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters (K&N, etc.) can cause the MAF to become dirty if the filter is over-oiled
There could be a vacuum leak downstream of the MAF sensor.
Intake manifold gaskets leaking


I clean my mass airflow sensor every oil change. Yet the screen is removed. I did block off the crankcase fresh air supply on the K&N tube, and now using a crankcase breather, that could possibly be considered "false air" not read by the MAF but I thought it would be so slight that the o2's would adjust.


While watching the info on my AutoXray.

idle hunts from 698rpm to 720rpm with 0% throttle position

MAF .51-.56lb/min

Ignition timing 15-17 degrees @ idle.... max of 45 degrees on rev

MAP 9in-hg to 10in-hg intake manifold vacuum @ idle, no voltage readings

Engine load @ idle 2.7%-3.1%

Engine coolant 183* (180 stat)

Bank 1 & 2 sensors 1 alternate between .065v - .850v, and my A/F gauge sweeps back in forth from lean to rich constantly.

9in of manifold vacuum seems low to me, I thought most engines idle around 18-20in manifold vacuum...I did not find any external vacuum leaks anywhere on the intake manifold/plenum/throttlebody but I won't rule it out.

Anyone have any ideas? What else causes a lean condition on both banks?

~Mykk

[04silveradomykk]

Holey crap, after some more search I found that it is my universal open element crankcase breather. That is exactly whats giving the p0171 & p0174. Damn!

[boxcarracer963]

is the breather those little mini intake style filters?

[04silveradomykk]

Yup, I went out and plugged in the AutoXray and watched my short term fuel trims at idle. First with the breather open and than with a plastic bag covering the breather.... open my short term fuel trim ranged from 4.6% to 8.5%. With the breather covered the STFT ranged from -2.4% to 2.3%... crazy

http://memimage.cardomain.net/member_images/11/web/2915000-2915999/2915246_1_full.jpg

[bespurcell]

That did'nt take you long to figure out.:)

[Mikz86TA]

So what does it all mean? That crank breather simply pulls air from the intake tube (originally) and allows the PCV valve on the other side to have fresh air. I dont see how if the intake tubes original port for the crankcase is plugged and essentially giving it a seperate filter affect fuel trims. I have the mod too and haven had those codes. I currently have the rear O2 or Catalyst Efficiency code. But I was told thats either a bad O2 or a bad Cat.

[Everfalling]

lol thanks mikz I thought maybe MYKK was going to answer his own questions before I got a chance to post whore ....hehe guess now it won't be a problem :)

[biglouie_underpressure]

45* of timing with nitrous?

[xacy0303]

I can't believe I see nitrous valves,cold air intake,e-fans,high performance coil, AND NO HEADERS! Where the headers man? I bet it would make your exhaust sound even nicer not mention the power increase.

[rat]

45* of timing with nitrous?

At part throttle yes. Full throttle is much much less than that. It would only have that much around 35kpa of vacuum.

http://thumb10.webshots.net/t/60/460/2/49/25/2024249250076568790HDGQsH_th.jpg (http://rides.webshots.com/photo/2024249250076568790HDGQsH)

[04silveradomykk]

I can't believe I see nitrous valves,cold air intake,e-fans,high performance coil, AND NO HEADERS! Where the headers man? I bet it would make your exhaust sound even nicer not mention the power increase.


The only one who makes headers for my application is JBA, and they're the shortie Cat4ward.... and they are bank!. My wet fogger nitrous system was cheaper (alot cheaper) than JBA Cat4ward headers, and I hear the gains are almost not even noticable.... If I did headers I'd go long tube, if I could find a pair that would fit.