So my 2003 str with 111k started showing bank 2 lean and restricted performance light is displayed. The code set is p0174 and pending is p0171 (Bank 1 lean) but never goes on even with multiple drive cycles. Car doesn't stumble, seems to be smooth. At highway speeds the restricted performance goes away. Looking the the fuel trim values after a full warm up I get this:

right off the highway in park at idle
lt ftrm1 = 17.2
st ftrm1 = 9.4
lt ftrm2 = 19.5
st ftrm2 = 20.3

in park at 2500rpm
lt ftrm1 = 3.9
st ftrm1 = 3.9
lt ftrm2 = 0
st ftrm2 = 14.8

in park at 2500rpm 2nd reading within 1 minute
lt ftrm1 = 3.9
st ftrm1 = 2.3
lt ftrm2 = 0
st ftrm2 = 13.3

in park at 2500rpm 3rd reading within 1 minute
lt ftrm1 = 2.3
st ftrm1 = 0.8
lt ftrm2 = 1.6
st ftrm2 = 0

back to idle in park
lt ftrm1 = 18.0
st ftrm1 = 0.8
lt ftrm2 = 19.5
st ftrm2 = 0

back to 2500rpm in park
lt ftrm1 = 3.9
st ftrm1 = 0.8
lt ftrm2 = 0
st ftrm2 = 8.6

2nd reading at 2500rpm within 1 minute
lt ftrm1 = 3.9
st ftrm1 = 3.1
lt ftrm2 = 0
st ftrm2 = 9.4

back to idle
lt ftrm1 = 18
st ftrm1 = 3.1
lt ftrm2 = 19.5
st ftrm2 = 14.8

Any insights? Valve cover? PCV?

Thank You.

 

Classic air leak. Affects both banks much the same so you can ignore any leaks which would affect only one bank. Go hunting. If you can get the display of LTFTs at idle where you can see them (ignore STFT) try spraying any burnable gas like propane cautiously - little squirts in different places. Common places for leaks are air flilter box & intake manifold but there are lots more vacuum lines.

 

As of right now both banks are lean. Codes set. I think it's the intake gasket below the s/c again. Sprayed break cleaner and the values change when I spray back of motor, front of motor.

Can't understand why the intake gasket failed again, after less than 2 years. Big job it is.

 

I would have to say the installation. We don't get reports of those gaskets failing at all. And guys that have fixed the under SC hose replace them too without problems.

Who did it and how much did they charge?
Were all new gaskets used or did the they reuse some?
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