I have a -00 charisma with 4g93 and the car suddenly started to misbehave while driving in -20 deg C weather. I diagnosed the car and it had 20 permanent fault codes that I'm not able to delete. Seems like all engine sensors have errors.

Is there any known issues that can explain this? Grounding issues, ecu problems, wiring harness problems?

 

With the temp's being pretty cold and the unrelated codes I would suspect a bad or weak battery first. Have you checked it yet? DON'T JUST REPLACE IT THOUGH!!! Have it tested.

 

The temperatures is now just below freezing. I also tried a different battery without success...

 

Next I'd check the cables, and ground.. Do a voltage drop test.

What codes did it set? Does the car actually run?

 

The car runs, it has idle but it is on/off. It varies between 800 and 1500 Rpms back and forth. When I try to rev it up, it barely hits 3000 Rpms. It runs very rich (the snow behind the exhaust is painted black)

I haven't really investigated the ground but I did try a to use a jumper cable as extra ground without noticing a difference.

I will try to write down all the fault codes next time I get a chance

 

Fault codes may help point in a specific direction...

Have you checked for a vacuum leak yet? I've seen that cause surging, though I don't know that it would set that many codes.