What Is Some Reasons That A Car May Idle Hard While Stopped In Drive

Posted in Internal Engine Parts

I drive an 03 Hyundai Sonata with a 4 cylinder engine. I was always told rough idling means it is time for new spark plugs. According to my maintenance schedule it is quite a while before I need to get new spark plugs (30,000 miles off)

What else could be the problem?
Thanks in advance
The AC does contribute to the rough idle, but I have driven with it off, and I still get the rough idle.

There are 6 Answers for "What Is Some Reasons That A Car May Idle Hard While Stopped In Drive"

    1. Pupmom says:

      The idel could be set to high from the last time it was serviced. It could need an oil change. it could be the cheep a$$ gas you might be putting in it. filters could be blocked. It could be a few things

    2. Cexsiman says:

      Rough idle can be cause by the AC believe it or not. if you are idling in a car with a small engine (less power) and the ac on, it puts a higher load on the engine at the already low RPMs and may idle rough. try turning the ac off at idle, it could be just how the car operates, and not be a problem at all

      it could also be that your idle is set too low. it is easily adjusted by a shop and would be a pretty cheap fix as well.

    3. Kost33ie says:

      It can be a few different things. I would start by buying a fuelcleaner that you can dump in your tank, just to flush out anything that may be in the lines. If that doesn’t do it check your ATF if its an automatic. If that all checks out then pull out one of the plugs and look for excessive burn marks, you should be able to tell if they are bad or not. If all that looks good get it into a shop. It could be your timing belt has slipped or something expensive.

    4. Loneranger72953 says:

      You may just have a bad plug or sparkplug wire. if you can pull each wire off one at a time and then replace it you should see a difference in the running if not then you know that plug is not firing as it should.

    5. Baldie says:

      Alot of things can do it, plugs can do it, plug wires can do it, vacuum leak can do it, a bad cap and rotor can do it.

    6. Mike M. says:

      30,000 miles is a long way off, but the problem you describe does sound like a tuneup is needed. The spark plugs are always in fire and literally burn up, then they can’t explode the gas in the engine with as much power. Idling doesn’t generate much power to start with, bad plugs reduce even that, the worst plug fails first, causing a limp or vibration, and Presto–not enough power to even keep the engine going by itself.

      This needs to be done every 25,000-30,000 miles, or you will lose power, burn more gas, fail emissions tests, and have it die on you unexpectedly. If you can’t remember when it was last done, I’d start there. And write it down and put it in the glove compartment, and write it on your calendar twice a year to check to make sure you don’t forget it. but of course, you should be getting a 30,000-mile service at 30k-60k-90k miles that includes it…

      My 87 Civic went 240,000 miles, dying only because I failed to change the timing belt, and whenever I thought it was dying it just needed a tuneup.

      Best regards,