So I have a 2005 Sentra 1.8S that's giving me issues.

I hadn't had it for long before I replaced the plugs and cleaned the throttle body unit because in gear it would idle around 500-600 rpm and was rough.. After doing so, I realized it was a mistake. The idle was erratic. I searched online and found the idle relearn procedure and did that which seemed to help somewhat. At least the idle wasn't up and down like it was before the relearn but still rough and low idle when in gear. I was ready to live with that and sell it that way until I noticed that when it's warm, it cranks forever to restart.

I searched this online and found that it's a fairly common issue with Nissan and their poorly made fuel pressure regulator.

I have been toying with it all afternoon and what it seems to be doing is I can hear the fuel pump energize intermittently. I will get it started and let it run for a few minutes. I will then shut it off and let it sit for 20 minutes or so then try to restart. Each time it takes forever cranking (but if I stop cranking and then turn the key off and back on and crank more, it starts right up). I just was out there with it and this time I noticed that the fuel pump was not energizing.

So... Fuel pump? Pressure regulator? Did I wreck the TB unit by spraying it with TB cleaner? Did I wreck the TPS switch by spraying? Is the hard starting not even related to my spraying the TB unit?

So many questions...

Always fully pressurize the fuel rail, prior to starting the engine. It sounds like the fuel rail is losing pressure, when the car sits. I always turn the ignition switch to ON, until the fuel pump stops running, before turning the key to start.

Check for vacuum leaks, especially around the intake manifold. With the engine running, spray water or brake cleaner, around the base of the intake manifold, and listen for changes in engine rpm. I would also ensure all air is properly purged from the cooling system--this can easily cause idle rpm to fluctuate. Did you clean the IACV and upper and lower ports, when you cleaned the throttle plate and throttle body?