did they show you any evidence of that? those stock bolts don't take much torque, but def. shouldn't be hand-tight. did they replace your water pump, at least? i'd expect more cam/crank codes if the timing were truly off. this engine ecu would've detected something being off. p0024 ain't it.

which O2? the fronts are wideband sensors and are critical for fuel control. rears are narrow-band, but can still screw with the fueling on this car. what is the actual code(s)?

5k for this job is straight up robbery, but you did take it to the stealership...

So the dealership it was at was an actual Nissan dealership. They did the worst job you can imagine with customer service and servicing the car. They did send me photos of the timing and the galley bolts loose but it's my word against theirs. Yes, water pump was replaced. With that said I would like to state that my regular mechanic drilled out the driver side cat as he stayed was extremely clogged. The codes that im looking at now may not be caused directly by this. CURRENT CODES ARE AS FOLLOWS: P0015 and P1168.

YOU DON'T NEED TO READ THIS BUT IF YOU WANT... I will also do a brief breakdown of how the dealership really screwed me over. After replacing the magnetic retarder my mechanic said to get it over to Nissan to make sure it didn't need a specific relearn and to make sure there wasn't any transmission issues. We were both at a loss. I did so and they charged me for 2 hours diag time and said were showing codes that point to timing. My mechanic said there were no codes.. I asked if this would fix the issue and they said yep. I needed a quote for the parts. They claimed they had to contact Infiniti directly in order to do any work. It's a nissan engine... After 4 weeks of back and forth and excuses to why the car wasn't done all of a sudden it was okay to use a kit I specify from the internet. Some time passes, they said it's ready. I go there and the car was hardly idling and there is no power steering fluid in the car as well as the check engine light flashing! I kinda lost my shyt and said fix it. I just paid them over 4k. It took them another 2 or 3 weeks to get it running to the point it's at now. The engine does sound nice but upon start it sometimes cranks a couple extra times and now it has that 1k rpm acceleration problem. Im located an hour away from the dealership so that made it a lot harder to get in their face about it. If you guys can give me an idea from here I would appreciate it. If someone knows how I can sue the shyt out of them for the hell they put me through please also chime in. Nissan and Infiniti corperate wont do ANYTHING. Sorry so long and sloppy....

is it p0015 and not p0051? from what i can tell, this is the driver side (bank 2) front sensor. replace it with an oem-like one (i guess, Denso). that should also resolve p1168 (open loop). but before replacing, double-check the fuses and make sure the sensor is actually plugged in (who knows what the dealer did while they were in there).

You are correct. The code is P0051.

get a new AF sensor (unless your current one is disconnected) and go from there.