02 Xterra Start and Die

I am helping a friend troubleshoot his 02 Xterra, and we are completely stumped and looking for advice

Vehicle: 2002 Nissan Xterra, ~140k miles, 3.3 V6-NA, Auto, 4WD

Issue: Starts immediately, runs smoothly for 2-3 secs and then dies. When it dies it acts like the key was shut down. No codes tripped and no codes showing pending. Seems to have good fuel and spark until it stops running.

Background: During a long road tip it started to have a lack of power once it was warmed up. The vehicle was towed to a mechanic who did some trouble shooting, and ended up cleaning the intake and MAF and running some intake fuel injector cleaner through the vehicle. This did not fix the issue, and was returned to the mechanic who proceeded to replace the distributor. Afterwards the vehicle ran well for a week or two, and then ended up with displaying the current issue, the start and then dying.

New Parts: Timing belt replaced less than 10k miles ago, Fuel Filter, MAF, Distributor, plugs, Plugwires, Fuel Sending Unit, Fuel Pump Relay, and a couple other relays.

Troubleshooting Done: Used a cheap code scanner to check for codes, Verified fuel pressure to fuel rail, verified voltage to fuel pump pre and post fuel pump relay, followed the FSM to check distributor (Coil and Cam values), FSM check on TPS, IAC (Fell outside of acceptable values, but not sure this would cause the issue), Checked voltage from key ignition, and a couple other things I am sure I am forgetting. Used starting fluid through a vacuum tube to the intake, and coaxed it to run roughly a few seconds longer. Rough timing check by linning the crank to TDC and checking the rotor position. Tried capturing coarse and fine cam signals and injector pulses using a Hantek 1008C, but couldnt save good data streams to really evaluate them. We recorded them on a cell phone, but this didnt work that well. We did manage to get the vehicle started yesterday after cranking the thing about 15-20 times while trying to capture the cam and injector waveforms. After it started we allowed the vehicle to warm up, and it seemed to run perfectly. Used the Hantek and saw very clean cam and injector signals which matched the drawings in the FSM and didnt show any weird behaviors. After warming the vehicle up, we shut it down and restarted it successfully multiple times. We allowed the vehicle about 30 minutes to cool down, and attempted a restart and it fired right up. The next morning the vehicle went back to not starting

I am looking for some advice on where to go with trouble shooting, even if that means going back and repeating anything already done with the exception of throwing random new parts at it. I am working on a way to do data collection from the Hantek in order to fully capture data from the failed start up attempts, but I am not sure how long that will take me to complete.

hi sir kind of a beginner I noticed there was no current measurement on fuel pump or the measurement of voltage on ground side I would try monitoring FP current and see what it does when engine cuts out

We might revisit the pump then. We did the electrical checks on the pump a couple months ago. If I remember right the resistance fell within spec which leads me to think as long as the voltage was right it should work. We did monitor fuel pressure at failure, and that stayed at spec.

Had this issue on my 05 pathfinder. Changed the crank position sensor and all was fine after that. I suggest going with the denso.

When it does NOT start or shuts down by itself, what is actually missing? Spark, inyector pulse, ckp signal? Knowing this is crucial for the diagnostic path to choose.

Regarding the crank sensor, the fan states it's only for tripping dtc codes in this generation x. We should take a peek at it since we haven't, and it's not working.

Not sure what is being cut at shut off. We have been somewhat lazy and not pulled a plug. How else can we tell what is being cut off. If you have a recommended troubleshooting flow I would love to see it and apply it to this problem.

Other info:
The cam position sensor provides two signals a coarse and fine signal. Both are essentially 5v pk square waves generated by an optical sensor. Coarse at I think every 120 degrees and fine every degree. While not running, the fine looked like it had a intermittent signal that poked up between the correct square pulses. We chalked that up to bad settings on the scope, and will likely attempt to recapture the. If I understand the fan right, during start up all 6 injectors are signaled together. Once it senses start it switches to sequentia. It seems as though at the switch point is when it shuts down. Side note, I figured out how to "record" the data stream from the Hantek. But it records basically as a movie and I can't really do any analysis (zoom, measure, adjust time base, etc). The data save on that cheap scope is basically only limited to what's on the screen.

I'd suggest trying to get a better idea what spark is doing when it starts, or starts and stalls. A test light on one of the distributor posts to check for spark strength during cranking is usually my go-to test. If you're by yourself, an in-line spark tester is another option.

FWIW, I had an '01 Xterra last month that exhibited similar symptoms, which I traced to a burned ignition coil inside the distributor. When the vehicle was cold, the spark would short through the coil case to ground instead of going through the cap/rotor/wires.

I see that the distributor was replaced and that the vehicle ran well for awhile, which leaves the possibility of bad parts.

Checked spark, and it is jumps about an inch. Pulled 3 of the plugs. They were dry and didn't look too terrible given the leaky valve seals. Cleaned them up with some 320 paper and it made no difference.

Next up is to check crank sensor, and revisit checking what the cam sensor and injectors are doing.

Any other thoughts?