GreenMtnSS

iTrader: (1)

Started driving the truck daily a couple weeks ago with the nice weather...mods are in sig.


Went to a shopping center, came out and left, on the way home CEL comes on.


Pulled codes when I got home. PO0172 and PO0174...Fuel Banks 1 and 2 running lean...


Cleaned MAF, checked all vacuum connections (replaced a vacuum cap that was dry rotted.)


Reset codes, ran fine for a day then threw the same code again.


AFR gauge reads between 14.5 and 15.3 during cruising, bottoms out at 10.0 whenever its in boost, and at idle in Park it will read 17-18.0 or max out AFR on lean side. A blip of the throttle will pull it down, then when it settles it maxes out again. Before this issue it would always be 14.3 during cruise, and 10.9 under boost, I've never seen AFR gauge go above 15, except when engine braking...


I have read that a leaking intake gasket will cause lean conditions, but would it be all of a sudden? Motor only has 10k miles on it...highly doubt its intake gasket.


Fuel pressure gauge reads 60psi constantly, so I feel like I can rule out fuel pump.


At this point I am hoping maybe its just bad gas? I use the same station and pump religiously...truck has been problem free for over a year with the blower.

What sensor or module causes the PCM to throw the codes I am experiencing?

I am looking for any kind of help to remedy this, let me know what you guys think.

brent1976

iTrader: (1)

Maybe an exhaust leak. That makes the O2 sensor think its lean so it ads more fuel at wot. That's why it lean at idle and rich when your on it.

SILVERADO11

Part 1 -Troubleshooting P0171 and P0174 (GM 4.3L, 5.0L, 5.7L)



Hope this helps, keep us posted on what you find.

GreenMtnSS

iTrader: (1)

That makes sense...but its lean on both banks, if it was lean on 1 bank it would make more sense...doubt it would be leaking on both sides all of a sudden, but its a possibility. I'll check it out. Thanks.

GreenMtnSS

iTrader: (1)

Very informative; thanks! I'll start this process when I get home from work!

GreenMtnSS

iTrader: (1)

So, in the process of trouble shooting vacuum leaks, I went to start the truck after messing with vacuum connections and it wouldn't start...Fuel pressure gauge read 0. I am pretty perturbed that the Aeromotive 340 pump only lasted a year. Had one overnighted from Summit...put it in, fuel pressure is back and seems to be running good. Cleared lean codes...now gotta put some miles on it to see if codes return or not, as clearing them before it would take a day or two for the codes to throw again. Hoping that was the problem...

Thanks for the help guys. Now I gotta contact Aeromotive to see what they can do...

GreenMtnSS

iTrader: (1)

So I am back to the drawing board...I have tried to fix or check everything that I think would cause this pig to run lean...changed throttle bodies, cleaned MAF sensor, took blower off of truck and cleaned and inspected everything. Made new gaskets for blower elbows, replaced fuel pump, fuel filter, and fuel pressure regulator. I have new spark plugs on the way...I know my plugs are gonna be pretty dark due to the PCM making the truck run richer than normal to compensate for the lean condition...

So what else should I check out? Intake gaskets? O2 sensors?

Here are my mods, for those guys on mobile...Kenne Bell 2.2L Twin Screw, FLT LVL 7, Circle D 258mm Multi Disc 3200 Converter, Tru Cool 40k, Siemens 60lb'ers Aeromotive 340, NGK TR6IX, 2006 E-Fans, OBX LT's cat delete, Magnaflow cat back, Baer BBK. Tuned by Slowhawk.

GreenMtnSS

iTrader: (1)

Would a data log help?

greasemykey

iTrader: (5)

had this issue with a 02 camaro ss. ended up being his oil leak killed both upstream O2's. replaced them and she ran like a lamb from a horny Amish man.

Gordy M

iTrader: (2)

Early O2's were not really made for E10+ gas, it would degrade the switch points within 5-8 years. Newer Delphi's were built to better withstand E10/E85 gas. If you still have the original front O2's, it might be worth the change.