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Discussion Starter · #1 ·
When in park while car is running or at stop light in drive, RPM will dip from 1000 to 500 or a little below. Shifting into neutral will make it stop. 2014 Optima LX. All new spark plugs and new MAP sensor and still same issue. No mass air flow sensor as far as I can tell. Any recommendations much appreciated before I go on an 8 hour trip next week.
 

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Happens occasionally on my 2011 except it tries to drop below idle. Dealer said about cleaning the throttle body.
 

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Are you saying that the idle is normally 1000 then drops to 500?
I'd check the idle rpm with a meter to be certain, but the 1000 is high and 500 is low.
 

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2021 Sorento EX T-GDI
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Is your AC compressor kicking on? If the compressor is bad it may cause a LOT of drag
 

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Discussion Starter · #5 ·
Are you saying that the idle is normally 1000 then drops to 500?
I'd check the idle rpm with a meter to be certain, but the 1000 is high and 500 is low.
My mistake, it will go from around 800 to below 500 and start to shake.
 

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Can I check this by cutting off the AC? I've tried with the AC on full blast and completely off.
Usually when you turn everything off, the electronic clutch for the air conditioner will disengage. This is just a shot in the dark though. Sounds a lot like an idle air control valve too but you know all cars are different so I'm not sure whats all on your engine.
 

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Discussion Starter · #8 ·
Usually when you turn everything off, the electronic clutch for the air conditioner will disengage. This is just a shot in the dark though. Sounds a lot like an idle air control valve too but you know all cars are different so I'm not sure whats all on your engine.
Don't think my car has an IAC valve, can't find the part. I'll try cleaning the throttle body and see how that helps.
 

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Can I check this by cutting off the AC? I've tried with the AC on full blast and completely off.
Usually when you turn everything off, the electronic clutch for the air conditioner will disengage. This is just a shot in the dark though. Sounds a lot like an idle air control valve too but you know all cars are different so I'm not sure whats all on your engine.
These cars have a VDC with no clutch. The A/C compressor internals are always turning even if the A/C is off.

Make certain the battery cables/terminals are clean and tight. May seem a stretch, but these cars with electronics are very critical to voltage.
Yerars ago worked on a '01 Jeep GC V-8, erratic idle, poor connection at battery, after cleaning fine.
 

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Discussion Starter · #10 ·
Code for the MAP sensor when hooked up to OBD2. Code P0106. Like I mentioned before, the map sensor is brand new.
 

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These cars dont have iac valves, you're correct or 3rd gens that i know of dont. Im kinda trying to figure this out too. But could be a few different things and one thing I've noticed is the car doesnt like non kia/Hyundai brand parts. If you didnt have a code before switching your map sensor I'd suggest putting the old one back in. Now for the rpm drop, ive been experimenting with the fuel pumps low and high pressure. I bought both from autozone and my car definitely did not like the high pressure pump (threw a code for regulator out of range [reg is built into high pres pump]), put the old one back on and code went away. As i said, get it straight from kia (online or in store). Back to self diag....low pressure was much much more difficult so i took a slight loss of power putting that one in and havent been able to replace it yet.
But long story short, check these parts
-Throttle body (give it a good clean)
-high pressure fuel pump (easy to replace, expensive)
-low pressure fuel pump (difficult to replace, expensive typically comes as full assembly including filter, etc)
-fuel injectors (my next attempt)
-Vacuum leaks (old lines get brittle and tend to fail)
-Sensors (Most usually don't fail so this is a rare case)
-spark plugs (the typical go-to for guessing through your wallet)

And of course anything dealing with fuel is very dangerous.
 

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Discussion Starter · #12 ·
These cars dont have iac valves, you're correct or 3rd gens that i know of dont. Im kinda trying to figure this out too. But could be a few different things and one thing I've noticed is the car doesnt like non kia/Hyundai brand parts. If you didnt have a code before switching your map sensor I'd suggest putting the old one back in. Now for the rpm drop, ive been experimenting with the fuel pumps low and high pressure. I bought both from autozone and my car definitely did not like the high pressure pump (threw a code for regulator out of range [reg is built into high pres pump]), put the old one back on and code went away. As i said, get it straight from kia (online or in store). Back to self diag....low pressure was much much more difficult so i took a slight loss of power putting that one in and havent been able to replace it yet.
But long story short, check these parts
-Throttle body (give it a good clean)
-high pressure fuel pump (easy to replace, expensive)
-low pressure fuel pump (difficult to replace, expensive typically comes as full assembly including filter, etc)
-fuel injectors (my next attempt)
-Vacuum leaks (old lines get brittle and tend to fail)
-Sensors (Most usually don't fail so this is a rare case)
-spark plugs (the typical go-to for guessing through your wallet)

And of course anything dealing with fuel is very dangerous.
Just to give a little update since I last posted on this thread, I've solved the problem.
Before going on an 8 hour trip for vacation, I cleaned my throttle body and battery terminals and cable connections. Battery looked fine, but I cleaned it anyways. Throttle body definitely needed the clean so it seems that's what really fixed the issue I was having.
By the way, I was getting the MAP sensor code before and after putting a new sensor in, so it's likely that I replaced it without neededing to at all.
Thanks for everyone's input!
 
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