I just cleaned my MAF sensor and (electronic) throttle body. After cleaning and re-installation, I performed the recommended throttle valve relearn procedures per the service manual, and went on my way; and the car runs better than ever. Idle at operating temperature is still a tad bit higher than normal, but I'm sure the computer will relearn it over time.
However, while I had my scanner plugged in after a short test drive, I noticed something strange: the spark advance value which, BEFORE the cleaning had typically hovered around 14°-16° degrees at idle (engine fully warmed up), was NOW hovering at around 3°-6° degrees (again, with the engine at operating temperature).
Thus, my question: why would this occur, and could it be indicative of another issue or set of issues? Vehicle in question is a 2002 Nissan Maxima with the 3.5L engine.
From what you've said, it sounds like you removed the throttle body from the engine bay. Maybe it's an issue with the throttle body position sensor (use a multimeter to test for that). I'm just guessing here, but a messed up throttle body position sensor would send grossly inaccurate data to the ECM, and that could be what's causing the spark degree differential.
I did disconnect it and remove it from the engine bay to clean it. TPS does seem like a potential cause; the car has about 103,500 miles on it and I doubt it's ever been touched. I'll grab a multimeter and do some looking around. Still odd to me that the car runs just fine, even with such a retarded spark advance, though...
The other thing I can think of goes to the sprays that were used. I'm assuming that you used the appropriate sprays (like CRC MAF spray) for the MAF and a throttle body (or carb clean) spray for the TB. But, maybe you should double check that . . . I've made inexplicable mistakes in the past (tired, distracted, just not paying enough attention). It happens, from time-to-time, to everyone.
I used CRC TB cleaner and CRC MAF sensor cleaner. I was very careful to avoid picking up the wrong can (to the point of even placing the TB cleaner a good 6 feet away from my working area while I was cleaning the MAF sensor).
Test the components. Here's a link on how to test a MAF sensor.
You can be rather scientistic about it. Test components, and if they test "as good," test their connectors (ground and power), check the wires, etc.