[lou-in-nj]

With both banks negative with similar values and no other DTCs I dont think its a leaky injector issue but I havent tried to test for that yet. Feels like they would all have to be failing at roughly the same rate to cause this and not have other issues.

Any ideas on other things that could be causing this condition?

Thanks
Brian

NO. Since your O2 sensor is reading a composite of the entire bank, all it takes is one bad injector on a bank to cause fuel trims to go down if it's leaking, or up if it's not spraying enough fuel. The question is, is it likely to have a bad injector on each bank at the exact same time? Remember, negative fuel trims mean the O2 sensor isn't sensing enough oxygen in the exhaust stream on average, especially when the computer is testing toward the lean condition, so the computer keeps cutting back on the fuel spray duration (which is what the trim number represents as negative trim), until the computer gets a reading from the O2 sensor that when the computer sends less fuel to the bank, the O2 sensor has a drop in voltage, indicating some oxygen is then present in the exhaust stream, and based on the voltage generated by the O2 sensor, the computer checks to see if it's in the correct range or not. You should run live data on the O2 sensor(s) and see what the voltage swings are...these swings should happen about 10 times per second and go from about 0.1v - 0.9v (the higher the voltage the less oxygen present in the exhaust stream.)

Vacuum leaks cause positive trim numbers, and I have yet to see an exhaust leak bad enough to cause O2 sensor reading issues, where you couldn't already hear your exhaust leaking. (I've had cracked exhaust manifolds that didn't throw off the O2 sensor.)

Now, how about your manifold tumbler flaps? I would think you should get a code for them not working right/not being in the correct position, but if they were stuck in a certain position, you might have a condition where your air flow is restricted to the point that the computer has to lean-out the engine. And since the flaps on both banks are typically linked together, this would cause the problem on both banks at the same time.

Fuel pressure could do it as well, but 5 psi high doesn't seem to be enough to make a difference.

 

[lou-in-nj]

Im starting to think my MAF reading is too high (even though I replaced it). My notes when this first started showed 3.4 g/s but now I get numbers like 4 to 4.7g/s at idle. Of course I first had the problem when it was running 3.4 at idle... Seems to show lower when warmed up and higher when at idle after just starting the car. If it thinks it has more air then it really does then the map is going to say to add too much fuel for the real amount of air. Causing it to run rich and causing the fuel trims to go negative to compensate. Does anyone know for sure what the MAF should read at idle?

Brian

You could try cleaning the MAF, watch this video:
Diagnosing a Faulty Mass Air Flow Sensor: P0171 P0174 Lean Codes
One thing this guy says to check is if you have any MAF reading with the engine not running ?
Also, DON'T buy no-name white-box parts from places like Amazon or eBay... Rockauto.com has a wide variety of parts brands available in almost every category. And even though Rockauto.com has a range of manufacturers for most parts, I've never seen any I would consider garbage...but still, you get what you pay for. I've saved upwards of 45% on the highest priced part over the same brand at the store. They even tell you which of their warehouses a part is located at, so you can buy other parts that are at that warehouse and minimize shipping cost. Put KLAVAN in the "where did you hear about us" box at check-out.

 

[lou-in-nj]

ALWAYS try replacing the vacuum lines first with these manifolds. I replaced the vacuum swirl-flap actuator which was broken as most people experience, but I still got errors, and later I discovered that the 14 year old vacuum lines were leaking enough to prevent full actuation of the vacuum actuators; once those were replaced, the errors went away.