My 1998 Forester has been idling really low, shaking while idling, and has the check engine light on. I took it on to my mechanic and he said it has been running on 3 cylinders rather than 4–what does that mean and is it expensive to fix?
It mean a multitude of things. Why has your mechanic given a real diagnosis of issue or is that still in process?
It means if your car was a dog with 4 legs, one of the legs is not working. So for your dog to run at full speed on 3 legs would not be as fast and as smooth as running on all 4 legs.
It is going to be expensive? If the problem is simple, a bad wire, bad coil, or bad spark plug on the cyclinder that is not working then the cost should not be too much. About $100 or less. If it is not simple, then it will cost much more depending on what the real problem. Perhaps you are not getting fuel to one cyclinder, could be simple or complex. Perhaps there is fuel and spark and not enough compression to fire the fuel. This could be a bad valve, or worn out rings. Definately expensive if you have low compression.
If you are not sure whether you trust the mechanic, before you OK a big repair bill take the car to a second mechanic for another opinion. If they agree you can decide which you trust more to do the work. If they disagree write back and tell give us more info and you’ll get more specific and useful advice.
Meanwhile, you should not drive this car very far until you know what is wrong and get it fixed. Running like this is rough on the motor. And it may be putting raw gas into your catalytic converter which will fail, clog up, and be another very expensive repair bill.
It means something is not working in your car. The fix could require anything from a little maintenance that may be past due anyway, to a new engine.
When was the last time the plugs and wires replaced. How about fuel and air filters, oil change. All those things and more need to be done on a regular schedule to avoid some expensive repairs.
Your mechanic can do some easy test to get a far better idea of what is going on.