Copied to from another thread on the same topic related to replacing O2 sensors and Crankshaft Position Sensor:
Re: 2004 FX45 (V8) O2 Sensor Discussion
Postby imnprsd » Sun Sep 25, 2022 2:05 pm
TO CONCLUDE: I openned this thread based on the goal of increasing MPG by replacing the Upstream 02 Sensors with the hope that would improve my city-MPG, and my journey has tought me several things:
1) This VK45DE (V8) in my 2004 FX45 is a pig when it comes to city MPG, albiet what's a 8MPG in this Infiniti I enjoy driving vs 12MPG-city I used to get in a V6 Honda. I mean who cares? s*** MPG is just that.
2) I found replacing the upstream O2 sensors was not as easy as I thought so I paid a shop to do it. $400 later, because they upcharged me, my city MPG is still in the toilet at 8MPG in heavy city driving, but my highway MPG is acceptable at 20-22MPG.
Would I recommend you replace your O2 sensors if you are getting 20-22MPG on the highway? ...No!
3) Would I recommend you replace your crank position sensor in you were not experiencing any no-start conditions? ...No!
Conclusions: It's all about weight vs. HP and you can't fight that. The only upside is that I may not end-up stranded on the side of the road anytime soon, because I elected to do some preventive maintenance (PM) by replacing my CKPS tend to fail somewhere between 120K-200K miles. And as for the 02 sensors getting replaced, that was a crap-shoot from the beginning and I lost.
So now my wallet is $600 lighter.
On my 2004 FX45 the CKPS was on the passenger side where the transmission mates with the engine block and not on the driver's side as implied in the video above. And I decided to us the OEM-Hitachi Part because Japanese cars tend to be finicky about sensors and coil packs. And the O2 sesnsor were NGK.
May thanks to VStar650CL weighing-in. I'm satisfied now.