What can be causing my cars rough idle, and vibration?

Question

My car is a 2002 Hyundai Elantra GLS. I found a couple bad, but not broken motor mounts and had them replaced, but my car still has a rough idle/vibration. My rpm was at 450 while idle, which was changed to about 700, but there's still a vibration. Had codes read and only code was the o2 sensor(I know it doesn't cause vibration). What should I look at? My engine and transmission are in good condition.

Update:

When the rpm was up to 700 the cars vibration slightly lessened

Update 2:

And is it possible it could be spark plugs, or air control valve related even though there's no codes

Evil C · Answer

Simplest thing to check first would be proper operation of the idle control valve. These valves are usually installed into the throttle body and they consist of a stepper motor, a cone shaped metering head, and a spring. The head and spring tend to get carbon buildup on them over time and require periodic cleaning for proper operation, or else they can bind up and not open or close properly, resulting in erratic and problematic idling behavior as you describe. You just simply need a can of carburetor cleaner and maybe a brass or nylon detailing brush to aid in cleaning the carbon off. I also recommend spraying out the cavity the valve installs into free of carbon deposits as well. Good luck.

mermeliz · Answer

Possible problem: 1. fouled or damaged spark plug - 2. fouled or bad fuel injector - 3. bad or loose spark plug wire - 4. bad harmonic balancer - 5. cracked block - 6. blown head gasket

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What can be causing my cars rough idle, and vibration?

2 Answers