So I have a 2005 g35x car sat for a bit me and a friend went to swap over my exhaust from my old g35 but got stuck on the header to cat bolts. I called a shop down the road to help us remove the bolts but I have to drive it there. We already removed the whole exhaust except the headers and cats. The down stream 02 are also unplugged we started the car up, started up no issues before I can get out of the drive way it died and it cranks but does not fire at all. Would the lack of exhaust and down stream 02 cause this or do I have another issue I have to look into.

 

You say it sat for a while. Did you run it at all before you started working on it? Was it working totally normally for however long you ran it before you started the exhaust work? I don't know if unplugging the downstream o2 sensor should keep it from running but seems simple enough to plug them back in to see. Probably easier to put enough of the exhaust back on to get the o2 sensors plugged in and into the exhaust stream before you start looking for other problems. If I mod something and it stops working, I usually put it back to stock as a sanity check to make sure it still works.

Crank no start is a fairly common problem situation so has fairly common debug strategy. I didn't search but there must be some good old threads where Cleric or somebody has walked somebody through a crank-no-start fix. First check for codes. If you have a U1000 on the main CAN network it probably won't start but you should have a check engine light and weird fan behavior. Is your immobilizer preventing starting (red key on the dashboard). Easiest thing to try is starter fluid in the airbox. If the car sat, do you KNOW the gas is good (starter fluid should help you figure this out). You can pull a plug and ground it to the engine to check for spark. Best to disable your fuel pump to do this by pulling the fuse. Do you see any rpm indication when you crank? I forget how many it should indicate but I'm pretty sure SOMETHING should be indicated when you're cranking if the crank sensor is working. There will be good threads with this kind of stuff if you look.

 

Ok so I figured out why it would not start I feel stupid but it had no gas despite the gauge saying it was half tank silly me. I now have motordyne plenum spacer berk hfc stillen true dual cat back z1 motor sports z tube and k&n filter. I keep getting code p1273 I checked my Inkake no leaks also no exhaust leaks. I plan on getting uprev tune soon because My fuel trims read lean of corse but I noticed my upstream 02 sensors don't fluctuate at idle they flat line around .3 and when I blip the throttle they jump a bit then flat line again. Is that normal I read it's supposed to jump around at idle I don't want to tune if there is another problem. Thanks for the response runs good though.

 

I had that same fuel gauge defect. Mine was DIY-able following a thread on here. Search "fuel gauge problem detailed" and it will come up. It's a long one but there is a post that details some resistors solder joints that need to be touched up.

 

Quick note that there are multiple ways that the fuel gauge can have problems. It might not be the cluster; could be other things. Best to follow the troubleshooting sequence in the FSM....

 

Good luck figuring out which section of the FSM to go to for troubleshooting the fuel gauge (it's the DI chapter). I recommend reading that thread even though it's hundreds of posts just so you see how many people replaced the sending units that weren't bad in case you're thinking of replacing those first without troubleshooting. And I'll bet 10 to 1 if your gauge reads full when you fill up and then never reads below half until the tank runs dry that the problem is with the resistors in the combo meter. Good luck and let us know what you find.

As far as the A/F sensor readings, I don't know what they're supposed to look like exactly and it depends on how responsive your tools are to see the changes. I have an old handheld obd reader that can display live data but the refresh rate is slow and probably misses alot. I had some logging software from when I got tuned that produces a much better chart but I don't remember what it looks like. I do recall some weird thing that one side reads 0.3V and the other 0.6V for some reason. This confused a lot of people and had people trying to debug the sensors when it's just how Nissan decided to report this info on those PIDs.