Lately my car has been idling really low like around 600 at startup. Give it a rev and it will go up and just fall quick to 0 and shudder and go back up. When the car starts like this and i drive it, every time i throw it into neutral the car idles bad and shudders. I can come back to the car an hr or so later and its fine. Even at start the car is fine sometimes. So sometime last week my car dies on me. I couldnt get the motor to run for a good 10 mins and then it finally started up but was shaking REALLY bad. I pull the code and its throwing a cel 45. I change the cap and rotor and for a week or so the car is fine. Perfect idle and good power. The other day i go out and get back in the car and it wont turn on. The car just stalled out as soon as it cranked. Check to see if the wires were loose and everything was fine. Go to pull the code and nothing comes up. Wait about an hr and the car starts up. Now the only problem is that is idles low but it never gets as low as before to the point where the car is shaking. Im so confused. Searched like a mad man and found some possible solutions but can someone help me to diagnose whats wrong with my car