1999 Lexus RX 300

Engine Performance problem
1999 Lexus RX 300 6 cyl

I'm working on a Lexus RX 300. It came in with a P0171 and P0325 code and the " Check Engine" light on. I put it on my Snap-On OBDII scanner and got a " Lean Mixture on Bank 1" code. I got the P0325 code off, but I can't solve the P0171 fault code. I feel like I've tried everything:

-Knock Sensor
-Oxygen Sensor
-PCV Valve
-Spark Plugs
-Upper Intake Manifold Gasket
-Lower Intake Manifold Gasket
-Coolant Temperature Sensor
-Traced every Vacuum Hose, check for leaks

After all of these repairs, the customer says it runs great, but I can't get the " Check Engine" light to stay off, on top of the stubborn P0171 fault code.

I don't suspect anything wrong with the EGR valve because it idles well. My scanner should give me a code as well. I don't suspect the MAF sensor either because again, no codes show up on my scanner.

Do you have any suggestions?
October 19, 2009.

Check out the related content below while we wait for the question to be answered by a professional mechanic.