2004 jeep liberty, 3.7 automatic. has a loud knock almost sounds like its coming from the intake, motor seems to run smooth, i dont believe it to be a rod or main. what else could it be? sometimes when i start it, i dont hear it all untill i give it a little throttle, then i becomes noticeable, and will do it even at idle.

SOURCE: 2004 stratus 2.7L Erratic idle, sometimes dies, sometimes revs at stops

hey-I have has this before different car but same - idle control valve is failing - computer at shop will pick this up on diagnostic

SOURCE: 2004 Dodge Stratus automatic has trouble shifting gears

I had the same problem - it was a fuse that controls the speedometer and the shifting solenoid

SOURCE: 2002 jeep liberty 3.7 engine where is knock sensor

get the pcm computer checked first for errors.
The 2 knock sensors are bolted into the cylinder block under the intake manifold. The sensors are used only with the 3.7L engine.
http://www.autozone.com/shopping/repairGuide.htm?pageId=0900c15280221909

what are your sysptoms of no start?

SOURCE: 06 dodge ram hemi engine knock at idle from bottom of engine

Sometimes a valve lifter will stick and cause a ticking it is possible that a valve lifter has lost its prime or it might be that the oil is too thin. Wthout more info my bet would be a lifter

SOURCE: 2002 jeep liberty code p171

looked up your code and it says that your bank 1 sensor 1, means you have more than 1 sensor, this one is for your fuel, says your mixture is lean, might need a tune up..or the sensor is bad..hope this helps....shia