Oscillating Idle - Kia Forum

 
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post #1 of 5 (permalink) Old 04-19-2019, 11:18 AM Thread Starter
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Oscillating Idle

I have a 2012 Sorento EX 3.5 Ltr (43K+) with an oscillating idle when in park, warm engine, no A/C on.
I had to have the throttle body (TB ) replaced recently due an issue with loss of power when cold.
The idling issue started before the TB was replaced (I was hoping this would have fixed the idle issue).
In park, the idle is fluctuating up & down about 100 RPM according to the Tach.

Reading some of the other questions from fellow members, one thing to check I've learned is to inspect vacuum lines and the Idle Air Control valve, to possibly clean it.
Does anyone know where the IAC is located on the V-6? I can't seem to locate it.

I've washed down the vacuum lines, and couldn't notice a difference in the idle while doing this (ie; no noticeable vacuum leak).

Any help would be appreciated. It's not causing me any grief, but more of an annoyance.

Thank you in advance.

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post #2 of 5 (permalink) Old 04-19-2019, 12:11 PM
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Normally I'd say the computer needs to relearn and adjust. This is a procedure that's done by the dealer (or whoever has the Kia diagnostic tools):

Kia Sorento: Adjustment - ETC (Electronic Throttle Control) System - Engine Control System - Engine Control / Fuel System - Kia Sorento XM 2011-2019 Service Manual

However, you said it was not idling properly before the throttle body was replaced. So it might not be this, but you should definitely confirm if it was done or not. Did they tell you what was wrong with the throttle body exactly? I would take it back to them, because the job really isn't done if they said "replacing the throttle body will fix your issues".

Finding the source of a fluctuating idle can be a real rabbit hole.. on these cars, the sensor is built into the throttle body assembly, so that's probably why they replaced the whole thing.

Also, this car doesn't have an IAC.. the ETC handles that (see the link in the manual above). Really, this isn't something you want to just start throwing non-returable parts at. And it's not likely something that will be resolved with a normal generic scan tool.
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post #3 of 5 (permalink) Old 04-19-2019, 02:20 PM Thread Starter
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Thanks for the reply rejesterd.
This problem was present before my TB problems.
The problem with the throttle body was a buildup of contamination in it. It was causing the engine to fall back to no more than an idle while trying to drive it, before a full warm up of the engine was done.

I actually watched the mechanic at the dealer try to clean it out, with the equipment & cleaners they had. Unfortunately their efforts
didn't resolve the problem. The issue with the TB was in the flap motor and/or controller on the side of it, which can't be accessed.
This is why it had to be replaced. Once done, and the relearning completed, it ran fine.

It wasn't till after I got the car back, I noticed the issue with the idle was still present.
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post #4 of 5 (permalink) Old 04-19-2019, 02:48 PM
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Gotcha.

If the spark plugs haven't been replaced, I would do that as a next step. That's something that would cause idle to jump and the check engine light probably wouldn't come on. But everything else (like the o2 sensor, MAP sensor, etc.) should cause an error code.

Aside from that, I'd take to an independent guy. You can end up chasing your tail for a long time.
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post #5 of 5 (permalink) Old 04-20-2019, 08:54 AM Thread Starter
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Thanks rejesterd. That's the next thing I plan to do.
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