2003 350z -> Car is an absolute POS, but seems to run OK. Shortly after buying it, it has issues and here is the full run down.

Initial problem:
Car will start after about 5-7 engine cranks and then it runs fine, but once you stop it, it will not start again. Wait about 2-3 hours, car will start and run fine. Code in car when checked, P0345. (Camshaft Position Sensor) My son is stranded several times. I know it is cranking too much to start...should start quicker.

What we did:
Decided that we’d change the oil, filter, and the plugs since the car was new to us. Pulled the plugs and all look relatively as expected with a whitish residue on them, a couple worse than others. Nothing looks crazy. Put in new plugs, do nothing else, and the car now starts every single time. (Still after 5-7 cranks, so not normal, but it works)

Next problem:
Car has a misfire under WOT (always was there from when we got it) and over some time the car begins to misfire at lower RPM. It’s develops misfire at 3k, car becomes useless really. Buy FIXD OBD2 scanner and scan get P0345 as only code.

What we did:
Ordered new sensors from Z1. Installed them both. Car does not work properly at all, it starts, idles absolutely terribly – and now the car actually throws BOTH P0344 and P0345. I put back the sensor I considered to be an assumed good (the passenger side CPS) and the car will start and run (still misfires) but now only throws P0345 code. Doesn’t seem to matter what sensor I have in the car on driver side, it still misfires and still throws code P0345.

I think maybe electrical problem. So I start looking deeper in to the connector on the driver side CPS sensor. I peel back all the wires and find that is has been spliced at some point. I’m thinking possibly that both my original driver side sensor and the Z1 sensor may be OK. And electrical problem is causing the code. I decide to start the car with the sensor not hooked up. It starts fine. Behaves the same way.

I decide to get a new harness clip so I go to the pick and pull and take a driver side sensor and plug from a 2003 Murano. I just rewire it in the same way, and hook it up to the new Z1 sensor. Now the car cranks, and will not start. I hook it up to the old sensor, and it will not start. I decide to try the sensor from the Murano. Now it starts and idles like absolute ****.

IMPORTANT NOTE: This is the last time this car starts.

What we did:
I decide that I've swapped sensors so many times and have had different results ... think wiring could be the real issue ... but I don't trust any of the CPS sensors. I buy new Hitachi sensors and take them out of the box and put them directly in the vehicle. Both sides. I decide that this will be considered two working sensors and any other issue is just that. These should be good sensors.

Car cranks, and will not start. I think it must have something to do with wiring. But my mechanic friends all tell me to take all the plugs out, do a compression test, leak down test, and get back to them with the numbers. Fine. I take all the plugs out, and I test all the coil packs while I am doing that. All test 1-2 at 1.40-1.45 and all test 1 to 3 and 2 to 3 at 3.21-3.27 on 1 3 5 and 2.94-2.97 on 2 4 6. I decide the coil packs are fine. When I am removing the spark plugs, which are of course very new, I see that most of them are soaked (fuel) and suspect with all the failed cranking we’ve done, the thing may be flooded. At this time my current plan is to do the compression test and put it back together and see if it starts. (As you will see, I don't get that far! read on!)

Next problem:
I get all the plugs out. I remove the fuse for the fuel pump. I’m now going to do a compression test. I put tester in plug 1, car cranks fine, get a reading of 150 cold but may have not cranked it long enough. I move to hole 2, car cranks fine, I get 160. I move to cylinder 3 and get 165. I decide I will test hole 1 again and let it turn over one more crank or so. When we do this, it doesn't work at all and the car suddenly sounds very sick, make a not very nice noise while turning over and you can tell it’s not cranking properly. We try a couple times but it sounds wrong and we stop.

What we did:
I try to jump it thinking maybe the battery is fubar from all this cranking it’s been doing with no actual engine ever running to charge the battery. This does nothing and the car still cranks with a not normal sound. I pull the battery out and see it is a pick n pull battery. I decide well, I’ll get a new one. We get a new battery, does the same thing. I disconnect negative terminal and stop. I create an account on my350z.com and post this thread! I mean, I'm giving as many details as possible...so...

THOUGHTS?

 

did you use OEM camshaft sensors... well documented on here that it only likes those

 

One thing I noticed is that you have not mentioned anything about the crankshaft position sensor?
Have you changed it?
That's the only thing I can think of that may be a problem, especially after all else you have done.
BTW, the reason I ask is that I had a problem similar to what you are experiencing, and finally changed the crankshaft sensor starting problem solved.
Hope this helps, let us know if you have any success.

 

This. The long crank is almost always the crankshaft position sensor.

 

I have not replaced that sensor, but certainly can.

But I'm most concerned right now about why the engine no longer cranks normally, very suddenly while in the midst of a compression test. A scenario where the engine really isn't under any load. I actually haven't even had time to look at the car since posting this. But I will be once it warms up a little. But yeah, I'll do that sensor and report back.