Hey guys, a few weeks ago I broke a valve spring on the pssenger side then sortly after the repairs were done I started getting the following code..

P0171 - Fuel Trim System Lean bank 1-B, Drivers side

After starting the car up, and allowing it to idle for about 2 minutes it immediately idles like ****, and throws the lean code.. The car runs fine in open loop, but once in closed loop, its runs like crap..

Current mods on my 2004 Z06 with 16,500miles:
Long Tube Headers, Tune, Vararam Intake, Crane Dual Springs, t-stat..

I removed the plugs, and found the drivers side to be completely black, and the passenger side spark plugs to be in good condition.. Im going to guess that while the car thought it was running lean it was running real rich (correct assumption?)

-I replaced the 02 sensors, code still present..
-I swapped the 02 sensor lines, and the code pops up on the drivers side no matter what.. (so the lines are safe, no issues with wiring)..
-I replaced the MAF, code still present..
-Opened up the ECU, no water present..
-Had a compression and leakdown test done on the car, results were perfect, motor is in great shape..
-I recently had my shop reflash the ecu so that I run the stock program after the header company suggested that it might be my tune.. Code still present..

I unplugged the front 02 sensors (so the car runs in open loop) and drove the car around and aside from running really rich, the car has no issues, runs pretty well.. With the 02 sensors plugged in up front, the car will stumble on its on with just a little throttle application, throws the lean code, misfire codes every so often, and seems like it wants to die.. At WOT, the car runs like crap..

Tonight I removed the drivers side header, and found the following.. I was just wondering if this was was a large enough crack to cause a lean code?

I really don't know what else to check after this (maybe injectors?).. There was no soot around the header/head connection, but to ensure its not a leaking gasket Im replacing the drivers side once I can get my hands on one... The headers have been on the car for over 6months, and never once gave me an issue and as far as I know were not removed during the valve spring repair..

I have been told that it was probably an exhaust leak which is why I pulled my headers off..

I have no more ideas left as to what can be causing a lean code to be thrown.. Remember, the lean code will get thrown with the car just sitting there at idle and does so once the car goes to closed loop.. It doesn't take any serious engine load to get the lean code.. Any help/suggestions are greatly appreciated.. I don't know what else to do, and the shops that Ive talked to are out of ideas..

Thanks..

 

I dont think something that small could cause the code, but it might.

Check the wires for cracks? Bad plug? Bad coil pack? Vacuume leak on aor around intake? TPS?

 

Oh.. I also swapped all the plug wires (drivers side to passenger side), and replaced the spark plugs.. The intake was check for leaks, and turned out to be okay..

As for th TPS (throttle positioning sensor..right?).. Just wondering - if that was bad wouldn't I be getting a lean code for both sides?

Guess I could have a bad injector.. Ill have to swap the drivers side with the passenger side and see if anything happens...

Also.. I guess I could also swap the coil packs.. Thats really not too difficult, I just figured that if it was an ignition problem, and I wasn't getting the required spark I would be throwing misfire codes, not a lean code... or have some people seen different?

 

try fuel filter. 9 times out of 10 this code is caused by a fuel filter that is plugged or restricted. when I see this code at work I put on a new fuel filter unless it has one, and $15 is cheap enough most customers don't mind paying for one even if it doesn't fix it. A fuel pump can cause this code if its not putting out enough pressure. If that doesn't fix it then you have a vacuum leak or possibly in injector problem (try the others first before going that route). It will not be a spark problem if spark was the problem you'd have a fuel trim rich code and a dead cylinder at almost all times. Its either lack of fuel or unmetered air (vacuum leak).

 

Not a likely cause for that code. If it is it could flag a code for one side or the other but not both. MAF, O2, IAT and MAP sensors are the main sensors that would affect this problem. Most of them will flag a code other than just a 171 when they have a problem.

Don't bother with the coil packs highly unlikely. Injector possibly but save it for later as the more likely possibilties are easier to test.

 

Thanks Cody, after the new gaskets are installed, I will give the fuel filter a try, and then its onto swapping the injectors..

 

Sounds like you might have a wiring problem with the drivers side 02. If you swapped the wires down below and the harness has a problem further up it won't matter.

 

I should probably clarified what I said.. I swapped the wires going to the 02 sensors.. When they were swapped... the new code displayed was P0174 (lean condition on passenger side)... So the ecu thought the passenger side was lean, but the wires were swapped so the passenger side wire was going to the drivers side, which means its not a wiring issue.. Sorry for the confusion..

 

I had some o2 codes thrown with hairline cracks on my LT collectors. I'm
sure after fixing the "holes" in your header the problem will go away. The o2
sensors are very sensitive.

 

I've got the same problem right now, and Im having a sort of burnt smell coming from my exhaust after a hard run. Im think it could be a clogged cat, is this a possibility?

 

If there is any unmetered air getting to the 02 sensors via a crack in the exhaust it can and will set a lean Bank1/2 sensor code. This is unrelated but my shop has seen a ton of this on 4.0l Jeep motors that all seem to crack their exhaust manifolds after 80-90K and low and behold we see them after they fail their emissions test because CO/HC numbers are way out of wack.....duhh cause they 02 sensor cannot correct for unmetered air in the exhaust system....good luck.