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

[Learning]

Today, I went to Auto Zone and had them tested my battery and voltage regulator and it was found that the alternator/voltage regulator was not charging at all (meter showed it was under 12 volts) and the battery was good but needed recharging (it was low in charge) despite I had it fully charged 2 weeks prior.
What puzzles me is that how could my car still be running with a dead alternator?
Years ago, while driving, my alternator suddenly went bad, all lights in and out started to dim and my car stopped running on the road. So now, with the alternator not working how could it be running all this this time?

[Ryann]

I would definitely replace it. Without any jacket over them the copper strands in the wire will corrode in the elements and lose their connections with each other, causing a lot of resistance, AKA a bad ground. This could be the source of your troubles.

When you replace it be sure to scrape off any paint or corrosion from the mounting surfaces, and spray some battery terminal protector on the cable ends after they're bolted on.

[Learning]

I would start here. Check connections at the battery, then move to the engine compartment. There's a ground strap at the front RH side of the engine that another m42 r3vster was having issues with just days ago.

Thanks Ryan,

Are you talking about the large/very thick ground strap underneath the car on the passenger side? My mechanic and I looked at it the other day and it was all naked because the rubber covering has already all dried up and broken/ peeled off exposing all the metal part of it. However, my mechanic told me that it was no problem/wouldn't affect anything and it wasn't necessary to replace it and so I haven't replaced it.

[Ryann]

Similar problem can be caused by bad grounds between the engine and body of the car.

I would start here. Check connections at the battery, then move to the engine compartment. There's a ground strap at the front RH side of the engine that another m42 r3vster was having issues with just days ago.

[tjts1]

No i didn't have the same problem with this car but I have with others. Have somebody with a multimeter check the voltage with the engine running. Either the cigarette lighter or the battery are fine places to check. Similar problem can be caused by bad grounds between the engine and body of the car.

[Learning]

Thanks tjts1,
How do I check the voltage at the cigarette lighter? Sorry, I'm not mechanically inclined at all.
That white BMW in your picture is exactly what I own now. :-)
Did you ever have similar problems like what I have now?

[tjts1]

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.

[Learning]

Good day fellows,

I have a 1991 BMW 318i, 4 cylinders, 1.8 liter, E30, and M42 engine

The problem: when engine is running at idle or running on the road, the temperature gauge bounces from the middle into red and stays on red but the car doesn't overheat. Engine running rich and also hesitates with this problem, but the hesitation happens intermittently. Also check engine light comes on intermittently whenever the car is hesitating or not hesitating. Replaced O2 sensor, spark plugs, fuel filter, checked fuel pump and pressure they're fine. Also replaced thermostat, coolant temperature sensor, and temperature sender/temperature sending unit but the problem persists. Could it be the Mass Air Flow Meter? With engine running, I tapped and also hit hard the MAF but didn't make any difference. The check engine light code says O2 sensor. Checked also for vacuum leaks but it's all fine. Also what boggles my mind is after driving the car for about 20 to 30 minutes to reach engine's normal operating temperature and I turn the engine off and put the ignition at the ON position (without engine running) the temperature shows the correct temperature where the temperature gauge sits perfectly in the middle where it should be with normal operating temperature, however, when I crank the engine the temperature gauge would jump pass the middle and into the 3/4 or red zone and stays there, but occasionally it might move back to 3/4 but most of the time stays in the red and the engine would intermittently hesitates sometimes badly, sometimes mildly, and sometimes not at all and the car would be lacking power and run very richly . I checked the battery, alternator, coolant system and they're all fine. I also already bled the cooling system.
I have taken this car to about 5 good mechanics and no one knew what the problem was.

Hope I can find the answer here.

Thanks very much in advance.

All the best,
Kenny