Q: Car will start but will not idle good

Hello. An idling issue can be caused by many different parts on your car. I would need to know if this occurred before you replaced all of these parts or if it occurred right after. If it was after then the work needs to be checked and the parts need to be checked to make sure that the correct plugs were used.

If this was occurring before the parts were replaced, then I would start by checking the throttle body. If it is dirty, then this will occur. If it is dirty I would clean it out fully and then retest it. If the problem persists then it can be a throttle position sensor or just about any of about a dozen other sensors. As that time I would install a scan tool and see if there are any codes and monitor all of the sensors to see if there are any that are not reading correctly. If those are also fine, then the compression needs to be checked as this can also be caused by a valve timing problem. If you are planning on having this looked at, consider YourMechanic, as a certified mechanic can come to your home or office to diagnose the idling problem and advise on repair.