A few months ago, my '00 Sentra developed a rough idle but I ignored it because it wasn’t too bad, until recently at least. It had been getting progressively worse so I went out and bought some CRC MAF cleaner, which solved the rough idle altogether for about a day. After doing some errands, I started the car but it was now stuck in limp home mode, not matter how much gas I gave it, she wouldn’t top 20 MPH and 2.5k revs. I bought a new MAF, and that made the problem worse: in any drive gears or reverse, when given any gas, the engine would stall and die but when in neutral, I can rev it as high as I want to. I reset the computer and cleaned the new sensor to no avail. After re-installing the old sensor (which was visibly broken, it was missing an entire wire assembly), it will run poorly but will now drive with some quirks, and I don’t trust it further than around the block.
My question is: with the new sensor, do I need an ECU reprogram, did I receive a bad sensor, or is there a compound problem? (I’ve heard with similar issues: bad alternator, bad TPS, bad IAC module, dirty IAC or TPS, clogged fuel filter, bad fuel pump, dirty air filter, among others.)