Temperature gauge spikes from middle into red and car intermittently hesitates.......

[fiftytakedowns]

Check the voltage at your cigarette lighter when this is happening. The car will do all sorts of weird shit if your alternator or voltage regulator are intermittently failing.

my cigarette lighter isnt even working FML

[///digitalme]

my cigarette lighter isnt even working FML

Have you checked the fuse? Mine didn't work I thought it just didn't work it was the fuse

[Learning]

It's been almost 2 months since I replaced the the ground wire, installed a new alternator, and also replaced the alternator ground wire with a thicker one. However, it feels like my car is not running as smooth as it should be although it's running very well. Lately, I've noticed the check engine light has been coming on frequently and blinking like a Christmas tree light. However, on certain days the CEL doesnt' come on at all. I've also noticed that the temperature gauge has been fluctuating back and forth but for a few millimeters only from the center line to the right and back to the center line again. Also, the little lights has been flickering. I sense that there is an inappropriate flow of voltage (there is voltage fluctuation) and that's why the problem. I replaced my old battery with a new one also about 2 months ago,
Hopefully, someone here can pinpoint what the problem is.

[Ryann]

Do the "stomp test" and tell us what codes you get.

[copied from e30world.com]
1. For safety reasons, put the transmission in neutral, and turn the ignition key to "On" position but do not start the car
2. In quick succession fully depress and release accelerator pedal 5 (five) times
3. After couple of seconds Check Engine light will blink once, and start to flash code(s)
4. All codes are composed of 4 digits (see table below). For example, code 1211 is represented as Blink, pause, Blink Blink, pause, Blink, pause, Blink
5. When code(s) start to repeat, all of them have been displayed

As previously mentioned you should also remove your gauge cluster and verify all connections.

[///digitalme]

check to see all the ground cables are clean and dry, my temp gauge moves all the time when it rains.

[Learning]

OK, I did the 'stomp test' and I got code 1222.
What exactly is the problem?

[Ryann]

1222 is an oxygen sensor lean code, which usually means you either have a fuel delivery problem or more likely a vacuum leak. Too much air, not enough fuel.

I'd guess this is probably unrelated to the electrical problems you're experiencing.

[Learning]

I checked months ago for a vacuum leak and found none.

In regards to a fuel delivery problem, could it be caused by a faulty fuel pump? Months ago (while my car was having the bad hesitation problem) I did a fuel pressure test and it was fine. I also replaced the fuel filter around that time.
Also checked the fuel pump relay and it was alright.

Could the problem caused by a bad oxygen sensor itself? When my car was hesitating badly and running rich, I thought it was caused by a faulty O2 sensor (because the code said so) and so I replaced it and yet the problem persisted continuously for about 5 months until I replaced the ground wire and solved the problem. Might the O2 sensor have been damaged by the bad hesitation problem that lasted for months?
My O2 sensor is still under warranty and so I can go exchange for a new one at no cost.

UPDATE: This afternoon I had my mechanic check the O2 sensor and it had some greenish and grayish colors and so we replaced it with a new one thinking it would solve the problem, however, the CEL was still blinking to my surprise.