Rough idle at stop light

charlieg · 11-04-2009, 02:06 PM

Just bought a 2003 Rio with 53000 miles. Noticed that while in Drive at a stop light or sign, it runs rough. It shakes the car. It seems to run fine otherwise.

RValeros · 11-04-2009, 09:21 PM

I noticed that you're from Florida. Does it run rough when you have the AC on? My 02 Rio will run a rough idle when I have the AC on. Otherwise, it's fine.

I'm from the Southwest area and until recently I was running the AC constantly.
Rough idle and all the rattles included until I switched the AC off.

If this isn't the case, you might want to check your plugs and plug wires and go from there.

jcwit · 11-05-2009, 06:32 AM

Have you replaced your plugs, or are you getting condensation water under your engine cover?

pulsar86 · 11-05-2009, 02:14 PM

Is the idle ok in neutral or park with your foot off the brake? If it is only rough with your foot on the brake you may have a vacuum leak in a line to the brake booster or a leaking booster diaphram. Try it in neutral with your foot on and off the brake if the idle is rough only with you foot on the brake, suspect leaking brake booster hoses or booster diaphram. You can check the booster by putting your foot hard on the brake and then starting the engine if ok the pedal will sink towards the floor when the engine starts as the booster gets vacuum from the inlet manifold. Best of luck.

charlieg · 11-06-2009, 09:46 PM

This car sat for awhile. We got an oil, oil filter, and air filter change. Seems to have helped. I did try the brake booster test. It seems fine. I think I will change the plugs and wires.

pulsar86 · 11-07-2009, 02:18 PM

If the car has sat for a while some of the vacuum hoses might be cracked, a cracked or loose fitting vacuum hose can cause a rough idle. also check that your idle speed is correct, if it is slow the extra load of sitting in drive might drop it further and cause the rough idle.

KiaMTBrider · 11-07-2009, 11:04 PM

My car is an 03 manual. My hoses are ok. Why would they crack just from sitting?

nstoolman1 · 11-07-2009, 11:46 PM

Smog will deteriorate rubber. Tires,hoses,wiperblades,rubber seals, all suffer the effects.

marty-mar · 03-24-2010, 07:55 AM

Hi all, new here. I just got an 05 Rio and have same issue with idle dropping to about 500 rpm at stops. No difference noted with compressor on/off. Car had regular oil changes from dealer, not sure about mx though. I was just wondering if it is easy to increase the idle rpm, seems to like rpms around 7-800. Thanks, trying to make sure car is ok for son as first car.

DavesSpectra · 03-24-2010, 09:51 AM

I've read a lot about KIAs running poorly around 50k miles that the cause was worn out spark plugs. I think the mind set of replace spark plugs at 100k still lives.

Also ....Very important!... be sure to measure the spark gap and re-gap plugs BEFORE installing them. Check the specs in the owner's manual. They may be gapped for a different engine. I also read that KIAs DON'T like platinum plugs.

Spark plug wires like "hoses" can degrade with time and can leak their high voltage to the engine or body frame causing poor idling.
Dave