OK I had a check engine light on and a high idle. Auto Zone said I had codes 171 and 174, told me to replace the MAF. I did so. The high idle turned into a very low idle about 500 RPM, and the codes are still being generated. Took it to the garage, they say I have a warped manifold. They want $500.00 to fix. Does this sound correct?
Telling you to replace the MAF sensor was poor advice.
The #1 O2 sensor compares the amount of oxygen in the exhaust stream compared to the amount of air the MAF sensor detects. If the O2 sensor detects a higher content of oxygen in the exhaust stream compared to what the MAF sensor detects, you’ll get this code.
So in this case, I would look for an intake leak somewhere after the MAF sensor. And it could be an intake manifold/gasket(s).
Tester
agreed,check the PCV hose for cracks.
out!