Rough idle when stopped

THOMAS SHEA

MEMBER
2005 KIA OPTIMA
2.4L
4 CYL
2WD
AUTOMATIC
105,000 MILES

Whenever the car is stopped after warming all the way up, the idling becomes very rough. Idling jumps between 700 rpm's and 1000 rpm's, causes vibration and a jerk. Happens in all gears, but "neutral" and "park" have less of a jerk, rpm's still jump. Take off seems very delayed too, while main driving still have the same power and feel. I replaced the Idle control valve, spark plugs, air filter, PCV valve and there is no check engine light. The airbag light did come on, around the same time, but do not think it is connected. Any help is welcomed.

Tuesday, December 26th, 2017 AT 2:58 PM

1 Reply

KHLOW2008

MECHANIC
41,814 POSTS

Hi Thomas,

You did not mention cleaning the throttle body, was that performed?
Erratic idling can be due to air leaks between the Mass Air Flow and throttle body, check and ensure air hose is in good condition with no vacuum leaks.
Check engine compression. If compression pressure differences between cylinders varies too much, engine would not be able to idle correctly.
Have the injectors tested, variances in injection volume is a possible cause for erratic idling.

K H Low

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Wednesday, December 27th, 2017 AT 8:55 PM