When to dump a car is a tough call to make. Factors like:
- Hassle of getting another car.
- Maybe some problems are just annoyances, but the car still drives, so one more fix will get it running again.
- Condition of car and value versus cost to fix it.
I say if it has more than one serious drivability or mechanical problems that potentially pose a safety issue, and are expensive fixes, that may be reason to just ditch the vehicle. Moreso if the car is in rough condition anyway. My family spent $1200 on a rebuilt transmission on a 10+ year old minivan last year simply because to replace the vehicle would cost MORE, the body is in pretty good shape, and the fix pretty much fully restored drivability.